[PATCH v4 0/8] Provide support for RMPREAD and a segmented RMP

[PATCH v4 0/8] Provide support for RMPREAD and a segmented RMP

[Tom Lendacky]

This series adds SEV-SNP support for a new instruction to read an RMP
entry and for a segmented RMP table.

The RMPREAD instruction is used to return information related to an RMP
entry in an architecturally defined format.

RMPREAD support is detected via CPUID 0x8000001f_EAX[21].

Segmented RMP support is a new way of representing the layout of an RMP
table. Initial RMP table support required the RMP table to be contiguous
in memory. RMP accesses from a NUMA node on which the RMP doesn't reside
can take longer than accesses from a NUMA node on which the RMP resides.
Segmented RMP support allows the RMP entries to be located on the same
node as the memory the RMP is covering, potentially reducing latency
associated with accessing an RMP entry associated with the memory. Each
RMP segment covers a specific range of system physical addresses.

Segmented RMP support is detected and established via CPUID and MSRs.

CPUID:
  - 0x8000001f_EAX[23]
    - Indicates support for segmented RMP

  - 0x80000025_EAX
    - [5:0]   : Minimum supported RMP segment size
    - [11:6]  : Maximum supported RMP segment size

  - 0x80000025_EBX
    - [9:0]   : Number of cacheable RMP segment definitions
    - [10]    : Indicates if the number of cacheable RMP segments is
                a hard limit

MSR:
  - 0xc0010132 (RMP_BASE)
    - Is identical to current RMP support

  - 0xc0010133 (RMP_END)
    - Should be in reset state if segmented RMP support is active

      For kernels that do not support segmented RMP, being in reset
      state allows the kernel to disable SNP support if the non-segmented
      RMP has not been allocated.

  - 0xc0010136 (RMP_CFG)
    - [0]    : Indicates if segmented RMP is enabled
    - [13:8] : Contains the size of memory covered by an RMP segment
               (expressed as a power of 2)

The RMP segment size defined in the RMP_CFG MSR applies to all segments
of the RMP. Therefore each RMP segment covers a specific range of system
physical addresses. For example, if the RMP_CFG MSR value is 0x2401, then
the RMP segment coverage value is 0x24 => 36, meaning the size of memory
covered by an RMP segment is 64GB (1 << 36). So the first RMP segment
covers physical addresses from 0 to 0xF_FFFF_FFFF, the second RMP segment
covers physical addresses from 0x10_0000_0000 to 0x1F_FFFF_FFFF, etc.

When a segmented RMP is enabled, RMP_BASE points to the RMP bookkeeping
area as it does today (16K in size). However, instead of RMP entries
beginning immediately after the bookkeeping area, there is a 4K RMP
segment table. Each entry in the table is 8-bytes in size:

  - [19:0]  : Mapped size (in GB)
              The mapped size can be less than the defined segment size.
              A value of zero, indicates that no RMP exists for the range
              of system physical addresses associated with this segment.
    [51:20] : Segment physical address
              This address is left shift 20-bits (or just masked when
              read) to form the physical address of the segment (1MB
              alignment).

The series is based off of and tested against the tip tree:
  https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master

  94559bac4d40 ("Merge branch into tip/master: 'x86/sev'")

---

Changes in v4:
- Change the structure name of the newly introduced RMPREAD state data
  to rmpread, to avoid churn around the renaming of the old rmpentry
  structure.
- Change the fam19h check to be explicit ZEN3/ZEN4 checks
- Unify the use of u64 for RMP-related values instead of using a mix of
  u64 and unsigned long.
- Fix the RMP segment end calculation in __snp_fixup_e820_tables().
- Minor message cleanups and code simplifications.

Changes in v3:
- Added RMP documentation

Changes in v2:
- Remove the self-describing check. The SEV firmware will ensure that
  all RMP segments are covered by RMP entries.
- Do not include RMP segments above maximum detected RAM address (64-bit
  MMIO) in the system RAM coverage check.
- Adjust new CPUID feature entries to match the change to how they are
  or are not presented to userspace.


Tom Lendacky (8):
  x86/sev: Prepare for using the RMPREAD instruction to access the RMP
  x86/sev: Add support for the RMPREAD instruction
  x86/sev: Require the RMPREAD instruction after Zen4
  x86/sev: Move the SNP probe routine out of the way
  x86/sev: Map only the RMP table entries instead of the full RMP range
  x86/sev: Treat the contiguous RMP table as a single RMP segment
  x86/sev: Add full support for a segmented RMP table
  x86/sev/docs: Document the SNP Reverse Map Table (RMP)

 .../arch/x86/amd-memory-encryption.rst        | 118 ++++
 arch/x86/include/asm/cpufeatures.h            |   2 +
 arch/x86/include/asm/msr-index.h              |   8 +-
 arch/x86/kernel/cpu/amd.c                     |   9 +-
 arch/x86/virt/svm/sev.c                       | 632 +++++++++++++++---
 5 files changed, 675 insertions(+), 94 deletions(-)

-- 
2.46.2

[PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Tom Lendacky]

The RMPREAD instruction returns an architecture defined format of an
RMP entry. This is the preferred method for examining RMP entries.

In preparation for using the RMPREAD instruction, convert the existing
code that directly accesses the RMP to map the raw RMP information into
the architecture defined format.

RMPREAD output returns a status bit for the 2MB region status. If the
input page address is 2MB aligned and any other pages within the 2MB
region are assigned, then 2MB region status will be set to 1. Otherwise,
the 2MB region status will be set to 0. For systems that do not support
RMPREAD, calculating this value would require looping over all of the RMP
table entries within that range until one is found with the assigned bit
set. Since this bit is not defined in the current format, and so not used
today, do not incur the overhead associated with calculating it.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/virt/svm/sev.c | 121 +++++++++++++++++++++++++++++-----------
 1 file changed, 87 insertions(+), 34 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 0ce17766c0e5..4d095affdb4d 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -30,6 +30,22 @@
 #include <asm/cmdline.h>
 #include <asm/iommu.h>
 
+/*
+ * The RMP entry format as returned by the RMPREAD instruction.
+ */
+struct rmpread {
+	u64 gpa;
+	u8  assigned		:1,
+	    rsvd1		:7;
+	u8  pagesize		:1,
+	    hpage_region_status	:1,
+	    rsvd2		:6;
+	u8  immutable		:1,
+	    rsvd3		:7;
+	u8  rsvd4;
+	u32 asid;
+} __packed;
+
 /*
  * The RMP entry format is not architectural. The format is defined in PPR
  * Family 19h Model 01h, Rev B1 processor.
@@ -270,48 +286,77 @@ static int __init snp_rmptable_init(void)
  */
 device_initcall(snp_rmptable_init);
 
-static struct rmpentry *get_rmpentry(u64 pfn)
+static struct rmpentry *__get_rmpentry(u64 pfn)
 {
-	if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
-		return ERR_PTR(-EFAULT);
-
-	return &rmptable[pfn];
-}
-
-static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
-{
-	struct rmpentry *large_entry, *entry;
-
-	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+	if (!rmptable)
 		return ERR_PTR(-ENODEV);
 
-	entry = get_rmpentry(pfn);
-	if (IS_ERR(entry))
-		return entry;
+	if (unlikely(pfn > rmptable_max_pfn))
+		return ERR_PTR(-EFAULT);
+
+	return rmptable + pfn;
+}
+
+static int get_rmpentry(u64 pfn, struct rmpread *entry)
+{
+	struct rmpentry *e;
+
+	e = __get_rmpentry(pfn);
+	if (IS_ERR(e))
+		return PTR_ERR(e);
+
+	/*
+	 * Map the RMP table entry onto the RMPREAD output format.
+	 * The 2MB region status indicator (hpage_region_status field) is not
+	 * calculated, since the overhead could be significant and the field
+	 * is not used.
+	 */
+	memset(entry, 0, sizeof(*entry));
+	entry->gpa       = e->gpa << PAGE_SHIFT;
+	entry->asid      = e->asid;
+	entry->assigned  = e->assigned;
+	entry->pagesize  = e->pagesize;
+	entry->immutable = e->immutable;
+
+	return 0;
+}
+
+static int __snp_lookup_rmpentry(u64 pfn, struct rmpread *entry, int *level)
+{
+	struct rmpread large_entry;
+	int ret;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return -ENODEV;
+
+	ret = get_rmpentry(pfn, entry);
+	if (ret)
+		return ret;
 
 	/*
 	 * Find the authoritative RMP entry for a PFN. This can be either a 4K
 	 * RMP entry or a special large RMP entry that is authoritative for a
 	 * whole 2M area.
 	 */
-	large_entry = get_rmpentry(pfn & PFN_PMD_MASK);
-	if (IS_ERR(large_entry))
-		return large_entry;
+	ret = get_rmpentry(pfn & PFN_PMD_MASK, &large_entry);
+	if (ret)
+		return ret;
 
-	*level = RMP_TO_PG_LEVEL(large_entry->pagesize);
+	*level = RMP_TO_PG_LEVEL(large_entry.pagesize);
 
-	return entry;
+	return 0;
 }
 
 int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
 {
-	struct rmpentry *e;
+	struct rmpread rmpread;
+	int ret;
 
-	e = __snp_lookup_rmpentry(pfn, level);
-	if (IS_ERR(e))
-		return PTR_ERR(e);
+	ret = __snp_lookup_rmpentry(pfn, &rmpread, level);
+	if (ret)
+		return ret;
 
-	*assigned = !!e->assigned;
+	*assigned = !!rmpread.assigned;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
@@ -324,18 +369,26 @@ EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
  */
 static void dump_rmpentry(u64 pfn)
 {
-	u64 pfn_i, pfn_end;
+	struct rmpread rmpread;
 	struct rmpentry *e;
-	int level;
+	u64 pfn_i, pfn_end;
+	int level, ret;
 
-	e = __snp_lookup_rmpentry(pfn, &level);
-	if (IS_ERR(e)) {
-		pr_err("Failed to read RMP entry for PFN 0x%llx, error %ld\n",
-		       pfn, PTR_ERR(e));
+	ret = __snp_lookup_rmpentry(pfn, &rmpread, &level);
+	if (ret) {
+		pr_err("Failed to read RMP entry for PFN 0x%llx, error %d\n",
+		       pfn, ret);
 		return;
 	}
 
-	if (e->assigned) {
+	if (rmpread.assigned) {
+		e = __get_rmpentry(pfn);
+		if (IS_ERR(e)) {
+			pr_err("Failed to read RMP contents for PFN 0x%llx, error %ld\n",
+			       pfn, PTR_ERR(e));
+			return;
+		}
+
 		pr_info("PFN 0x%llx, RMP entry: [0x%016llx - 0x%016llx]\n",
 			pfn, e->lo, e->hi);
 		return;
@@ -356,9 +409,9 @@ static void dump_rmpentry(u64 pfn)
 		pfn, pfn_i, pfn_end);
 
 	while (pfn_i < pfn_end) {
-		e = __snp_lookup_rmpentry(pfn_i, &level);
+		e = __get_rmpentry(pfn_i);
 		if (IS_ERR(e)) {
-			pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",
+			pr_err("Error %ld reading RMP contents for PFN 0x%llx\n",
 			       PTR_ERR(e), pfn_i);
 			pfn_i++;
 			continue;
-- 
2.46.2

[PATCH v4 2/8] x86/sev: Add support for the RMPREAD instruction

[Tom Lendacky]

The RMPREAD instruction returns an architecture defined format of an
RMP table entry. This is the preferred method for examining RMP entries.

The instruction is advertised in CPUID 0x8000001f_EAX[21]. Use this
instruction when available.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/virt/svm/sev.c            | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 913fd3a7bac6..89c1308cdf54 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -448,6 +448,7 @@
 #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* Virtual TSC_AUX */
 #define X86_FEATURE_SME_COHERENT	(19*32+10) /* AMD hardware-enforced cache coherency */
 #define X86_FEATURE_DEBUG_SWAP		(19*32+14) /* "debug_swap" AMD SEV-ES full debug state swap support */
+#define X86_FEATURE_RMPREAD		(19*32+21) /* RMPREAD instruction */
 #define X86_FEATURE_SVSM		(19*32+28) /* "svsm" SVSM present */
 
 /* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 4d095affdb4d..e197610b4eed 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -301,6 +301,17 @@ static int get_rmpentry(u64 pfn, struct rmpread *entry)
 {
 	struct rmpentry *e;
 
+	if (cpu_feature_enabled(X86_FEATURE_RMPREAD)) {
+		int ret;
+
+		asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfd"
+			     : "=a" (ret)
+			     : "a" (pfn << PAGE_SHIFT), "c" (entry)
+			     : "memory", "cc");
+
+		return ret;
+	}
+
 	e = __get_rmpentry(pfn);
 	if (IS_ERR(e))
 		return PTR_ERR(e);
-- 
2.46.2

[PATCH v4 3/8] x86/sev: Require the RMPREAD instruction after Zen4

[Tom Lendacky]

Limit usage of the non-architectural RMP format to Zen3/Zen4 processors.
The RMPREAD instruction, with architectural defined output, is available
and should be used for RMP access beyond Zen4.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kernel/cpu/amd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index fab5caec0b72..547bcdf50f1b 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -355,10 +355,15 @@ static void bsp_determine_snp(struct cpuinfo_x86 *c)
 		/*
 		 * RMP table entry format is not architectural and is defined by the
 		 * per-processor PPR. Restrict SNP support on the known CPU models
-		 * for which the RMP table entry format is currently defined for.
+		 * for which the RMP table entry format is currently defined or for
+		 * processors which support the architecturally defined RMPREAD
+		 * instruction.
 		 */
 		if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
-		    c->x86 >= 0x19 && snp_probe_rmptable_info()) {
+		    (cpu_feature_enabled(X86_FEATURE_ZEN3) ||
+		     cpu_feature_enabled(X86_FEATURE_ZEN4) ||
+		     cpu_feature_enabled(X86_FEATURE_RMPREAD)) &&
+		    snp_probe_rmptable_info()) {
 			cc_platform_set(CC_ATTR_HOST_SEV_SNP);
 		} else {
 			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
-- 
2.46.2

[PATCH v4 4/8] x86/sev: Move the SNP probe routine out of the way

[Tom Lendacky]

To make patch review easier for the segmented RMP support, move the SNP
probe function out from in between the initialization-related routines.

No functional change.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/virt/svm/sev.c | 60 ++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index e197610b4eed..d0fca9bb2e12 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -132,36 +132,6 @@ static __init void snp_enable(void *arg)
 	__snp_enable(smp_processor_id());
 }
 
-#define RMP_ADDR_MASK GENMASK_ULL(51, 13)
-
-bool snp_probe_rmptable_info(void)
-{
-	u64 rmp_sz, rmp_base, rmp_end;
-
-	rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
-	rdmsrl(MSR_AMD64_RMP_END, rmp_end);
-
-	if (!(rmp_base & RMP_ADDR_MASK) || !(rmp_end & RMP_ADDR_MASK)) {
-		pr_err("Memory for the RMP table has not been reserved by BIOS\n");
-		return false;
-	}
-
-	if (rmp_base > rmp_end) {
-		pr_err("RMP configuration not valid: base=%#llx, end=%#llx\n", rmp_base, rmp_end);
-		return false;
-	}
-
-	rmp_sz = rmp_end - rmp_base + 1;
-
-	probed_rmp_base = rmp_base;
-	probed_rmp_size = rmp_sz;
-
-	pr_info("RMP table physical range [0x%016llx - 0x%016llx]\n",
-		rmp_base, rmp_end);
-
-	return true;
-}
-
 static void __init __snp_fixup_e820_tables(u64 pa)
 {
 	if (IS_ALIGNED(pa, PMD_SIZE))
@@ -286,6 +256,36 @@ static int __init snp_rmptable_init(void)
  */
 device_initcall(snp_rmptable_init);
 
+#define RMP_ADDR_MASK GENMASK_ULL(51, 13)
+
+bool snp_probe_rmptable_info(void)
+{
+	u64 rmp_sz, rmp_base, rmp_end;
+
+	rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
+	rdmsrl(MSR_AMD64_RMP_END, rmp_end);
+
+	if (!(rmp_base & RMP_ADDR_MASK) || !(rmp_end & RMP_ADDR_MASK)) {
+		pr_err("Memory for the RMP table has not been reserved by BIOS\n");
+		return false;
+	}
+
+	if (rmp_base > rmp_end) {
+		pr_err("RMP configuration not valid: base=%#llx, end=%#llx\n", rmp_base, rmp_end);
+		return false;
+	}
+
+	rmp_sz = rmp_end - rmp_base + 1;
+
+	probed_rmp_base = rmp_base;
+	probed_rmp_size = rmp_sz;
+
+	pr_info("RMP table physical range [0x%016llx - 0x%016llx]\n",
+		rmp_base, rmp_end);
+
+	return true;
+}
+
 static struct rmpentry *__get_rmpentry(u64 pfn)
 {
 	if (!rmptable)
-- 
2.46.2

[PATCH v4 5/8] x86/sev: Map only the RMP table entries instead of the full RMP range

[Tom Lendacky]

In preparation for support of a segmented RMP table, map only the RMP
table entries. The RMP bookkeeping area is only ever accessed when
first enabling SNP and does not need to remain mapped. To accomplish
this, split the initialization of the RMP bookkeeping area and the
initialization of the RMP entry area. The RMP bookkeeping area will be
mapped only while it is being initialized.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/virt/svm/sev.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index d0fca9bb2e12..dd256e76e443 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -168,6 +168,23 @@ void __init snp_fixup_e820_tables(void)
 	__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
 }
 
+static bool __init init_rmptable_bookkeeping(void)
+{
+	void *bk;
+
+	bk = memremap(probed_rmp_base, RMPTABLE_CPU_BOOKKEEPING_SZ, MEMREMAP_WB);
+	if (!bk) {
+		pr_err("Failed to map RMP bookkeeping area\n");
+		return false;
+	}
+
+	memset(bk, 0, RMPTABLE_CPU_BOOKKEEPING_SZ);
+
+	memunmap(bk);
+
+	return true;
+}
+
 /*
  * Do the necessary preparations which are verified by the firmware as
  * described in the SNP_INIT_EX firmware command description in the SNP
@@ -205,12 +222,17 @@ static int __init snp_rmptable_init(void)
 		goto nosnp;
 	}
 
-	rmptable_start = memremap(probed_rmp_base, probed_rmp_size, MEMREMAP_WB);
+	/* Map only the RMP entries */
+	rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ,
+				  probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ,
+				  MEMREMAP_WB);
 	if (!rmptable_start) {
 		pr_err("Failed to map RMP table\n");
 		goto nosnp;
 	}
 
+	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
+
 	/*
 	 * Check if SEV-SNP is already enabled, this can happen in case of
 	 * kexec boot.
@@ -219,7 +241,14 @@ static int __init snp_rmptable_init(void)
 	if (val & MSR_AMD64_SYSCFG_SNP_EN)
 		goto skip_enable;
 
-	memset(rmptable_start, 0, probed_rmp_size);
+	/* Zero out the RMP bookkeeping area */
+	if (!init_rmptable_bookkeeping()) {
+		memunmap(rmptable_start);
+		goto nosnp;
+	}
+
+	/* Zero out the RMP entries */
+	memset(rmptable_start, 0, rmptable_size);
 
 	/* Flush the caches to ensure that data is written before SNP is enabled. */
 	wbinvd_on_all_cpus();
@@ -230,9 +259,6 @@ static int __init snp_rmptable_init(void)
 	on_each_cpu(snp_enable, NULL, 1);
 
 skip_enable:
-	rmptable_start += RMPTABLE_CPU_BOOKKEEPING_SZ;
-	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
-
 	rmptable = (struct rmpentry *)rmptable_start;
 	rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry) - 1;
 
-- 
2.46.2

[PATCH v4 6/8] x86/sev: Treat the contiguous RMP table as a single RMP segment

[Tom Lendacky]

In preparation for support of a segmented RMP table, treat the contiguous
RMP table as a segmented RMP table with a single segment covering all
of memory. By treating a contiguous RMP table as a single segment, much
of the code that initializes and accesses the RMP can be re-used.

Segmented RMP tables can have up to 512 segment entries. Each segment
will have metadata associated with it to identify the segment location,
the segment size, etc. The segment data and the physical address are used
to determine the index of the segment within the table and then the RMP
entry within the segment. For an actual segmented RMP table environment,
much of the segment information will come from a configuration MSR. For
the contiguous RMP, though, much of the information will be statically
defined.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/virt/svm/sev.c | 193 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 174 insertions(+), 19 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index dd256e76e443..043b2582e10e 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -18,6 +18,7 @@
 #include <linux/cpumask.h>
 #include <linux/iommu.h>
 #include <linux/amd-iommu.h>
+#include <linux/nospec.h>
 
 #include <asm/sev.h>
 #include <asm/processor.h>
@@ -74,12 +75,42 @@ struct rmpentry {
  */
 #define RMPTABLE_CPU_BOOKKEEPING_SZ	0x4000
 
+/*
+ * For a non-segmented RMP table, use the maximum physical addressing as the
+ * segment size in order to always arrive at index 0 in the table.
+ */
+#define RMPTABLE_NON_SEGMENTED_SHIFT	52
+
+struct rmp_segment_desc {
+	struct rmpentry *rmp_entry;
+	u64 max_index;
+	u64 size;
+};
+
+/*
+ * Segmented RMP Table support.
+ *   - The segment size is used for two purposes:
+ *     - Identify the amount of memory covered by an RMP segment
+ *     - Quickly locate an RMP segment table entry for a physical address
+ *
+ *   - The RMP segment table contains pointers to an RMP table that covers
+ *     a specific portion of memory. There can be up to 512 8-byte entries,
+ *     one pages worth.
+ */
+static struct rmp_segment_desc **rmp_segment_table __ro_after_init;
+static unsigned int rst_max_index __ro_after_init = 512;
+
+static u64 rmp_segment_size_max;
+static unsigned int rmp_segment_coverage_shift;
+static u64 rmp_segment_coverage_size;
+static u64 rmp_segment_coverage_mask;
+#define RST_ENTRY_INDEX(x)	((x) >> rmp_segment_coverage_shift)
+#define RMP_ENTRY_INDEX(x)	((u64)(PHYS_PFN((x) & rmp_segment_coverage_mask)))
+
 /* Mask to apply to a PFN to get the first PFN of a 2MB page */
 #define PFN_PMD_MASK	GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)
 
 static u64 probed_rmp_base, probed_rmp_size;
-static struct rmpentry *rmptable __ro_after_init;
-static u64 rmptable_max_pfn __ro_after_init;
 
 static LIST_HEAD(snp_leaked_pages_list);
 static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
@@ -185,6 +216,92 @@ static bool __init init_rmptable_bookkeeping(void)
 	return true;
 }
 
+static bool __init alloc_rmp_segment_desc(u64 segment_pa, u64 segment_size, u64 pa)
+{
+	struct rmp_segment_desc *desc;
+	void *rmp_segment;
+	u64 rst_index;
+
+	/* Validate the RMP segment size */
+	if (segment_size > rmp_segment_size_max) {
+		pr_err("Invalid RMP size (%#llx) for configured segment size (%#llx)\n",
+		       segment_size, rmp_segment_size_max);
+		return false;
+	}
+
+	/* Validate the RMP segment table index */
+	rst_index = RST_ENTRY_INDEX(pa);
+	if (rst_index >= rst_max_index) {
+		pr_err("Invalid RMP segment base address (%#llx) for configured segment size (%#llx)\n",
+		       pa, rmp_segment_coverage_size);
+		return false;
+	}
+	rst_index = array_index_nospec(rst_index, rst_max_index);
+
+	if (rmp_segment_table[rst_index]) {
+		pr_err("RMP segment descriptor already exists at index %llu\n", rst_index);
+		return false;
+	}
+
+	/* Map the RMP entries */
+	rmp_segment = memremap(segment_pa, segment_size, MEMREMAP_WB);
+	if (!rmp_segment) {
+		pr_err("Failed to map RMP segment addr 0x%llx size 0x%llx\n",
+		       segment_pa, segment_size);
+		return false;
+	}
+
+	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+	if (!desc) {
+		memunmap(rmp_segment);
+		return false;
+	}
+
+	desc->rmp_entry = rmp_segment;
+	desc->max_index = segment_size / sizeof(*desc->rmp_entry);
+	desc->size = segment_size;
+
+	/* Add the segment descriptor to the table */
+	rmp_segment_table[rst_index] = desc;
+
+	return true;
+}
+
+static void __init free_rmp_segment_table(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < rst_max_index; i++) {
+		struct rmp_segment_desc *desc;
+
+		desc = rmp_segment_table[i];
+		if (!desc)
+			continue;
+
+		memunmap(desc->rmp_entry);
+
+		kfree(desc);
+	}
+
+	free_page((unsigned long)rmp_segment_table);
+
+	rmp_segment_table = NULL;
+}
+
+static bool __init alloc_rmp_segment_table(void)
+{
+	struct page *page;
+
+	/* Allocate the table used to index into the RMP segments */
+	page = alloc_page(__GFP_ZERO);
+	if (!page)
+		return false;
+
+	rmp_segment_table = page_address(page);
+
+	return true;
+}
+
 /*
  * Do the necessary preparations which are verified by the firmware as
  * described in the SNP_INIT_EX firmware command description in the SNP
@@ -192,8 +309,8 @@ static bool __init init_rmptable_bookkeeping(void)
  */
 static int __init snp_rmptable_init(void)
 {
-	u64 max_rmp_pfn, calc_rmp_sz, rmptable_size, rmp_end, val;
-	void *rmptable_start;
+	u64 max_rmp_pfn, calc_rmp_sz, rmptable_segment, rmptable_size, rmp_end, val;
+	unsigned int i;
 
 	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
@@ -222,17 +339,18 @@ static int __init snp_rmptable_init(void)
 		goto nosnp;
 	}
 
+	if (!alloc_rmp_segment_table())
+		goto nosnp;
+
 	/* Map only the RMP entries */
-	rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ,
-				  probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ,
-				  MEMREMAP_WB);
-	if (!rmptable_start) {
-		pr_err("Failed to map RMP table\n");
+	rmptable_segment = probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ;
+	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
+
+	if (!alloc_rmp_segment_desc(rmptable_segment, rmptable_size, 0)) {
+		free_rmp_segment_table();
 		goto nosnp;
 	}
 
-	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
-
 	/*
 	 * Check if SEV-SNP is already enabled, this can happen in case of
 	 * kexec boot.
@@ -243,12 +361,20 @@ static int __init snp_rmptable_init(void)
 
 	/* Zero out the RMP bookkeeping area */
 	if (!init_rmptable_bookkeeping()) {
-		memunmap(rmptable_start);
+		free_rmp_segment_table();
 		goto nosnp;
 	}
 
 	/* Zero out the RMP entries */
-	memset(rmptable_start, 0, rmptable_size);
+	for (i = 0; i < rst_max_index; i++) {
+		struct rmp_segment_desc *desc;
+
+		desc = rmp_segment_table[i];
+		if (!desc)
+			continue;
+
+		memset(desc->rmp_entry, 0, desc->size);
+	}
 
 	/* Flush the caches to ensure that data is written before SNP is enabled. */
 	wbinvd_on_all_cpus();
@@ -259,9 +385,6 @@ static int __init snp_rmptable_init(void)
 	on_each_cpu(snp_enable, NULL, 1);
 
 skip_enable:
-	rmptable = (struct rmpentry *)rmptable_start;
-	rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry) - 1;
-
 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);
 
 	/*
@@ -282,6 +405,17 @@ static int __init snp_rmptable_init(void)
  */
 device_initcall(snp_rmptable_init);
 
+static void set_rmp_segment_info(unsigned int segment_shift)
+{
+	rmp_segment_coverage_shift = segment_shift;
+	rmp_segment_coverage_size  = 1ULL << rmp_segment_coverage_shift;
+	rmp_segment_coverage_mask  = rmp_segment_coverage_size - 1;
+
+	/* Calculate the maximum size an RMP can be (16 bytes/page mapped) */
+	rmp_segment_size_max = PHYS_PFN(rmp_segment_coverage_size);
+	rmp_segment_size_max <<= 4;
+}
+
 #define RMP_ADDR_MASK GENMASK_ULL(51, 13)
 
 bool snp_probe_rmptable_info(void)
@@ -303,6 +437,11 @@ bool snp_probe_rmptable_info(void)
 
 	rmp_sz = rmp_end - rmp_base + 1;
 
+	/* Treat the contiguous RMP table as a single segment */
+	rst_max_index = 1;
+
+	set_rmp_segment_info(RMPTABLE_NON_SEGMENTED_SHIFT);
+
 	probed_rmp_base = rmp_base;
 	probed_rmp_size = rmp_sz;
 
@@ -314,13 +453,29 @@ bool snp_probe_rmptable_info(void)
 
 static struct rmpentry *__get_rmpentry(u64 pfn)
 {
-	if (!rmptable)
+	struct rmp_segment_desc *desc;
+	u64 paddr, rst_index, segment_index;
+
+	if (!rmp_segment_table)
 		return ERR_PTR(-ENODEV);
 
-	if (unlikely(pfn > rmptable_max_pfn))
+	paddr = pfn << PAGE_SHIFT;
+
+	rst_index = RST_ENTRY_INDEX(paddr);
+	if (unlikely(rst_index >= rst_max_index))
+		return ERR_PTR(-EFAULT);
+	rst_index = array_index_nospec(rst_index, rst_max_index);
+
+	desc = rmp_segment_table[rst_index];
+	if (unlikely(!desc))
 		return ERR_PTR(-EFAULT);
 
-	return rmptable + pfn;
+	segment_index = RMP_ENTRY_INDEX(paddr);
+	if (unlikely(segment_index >= desc->max_index))
+		return ERR_PTR(-EFAULT);
+	segment_index = array_index_nospec(segment_index, desc->max_index);
+
+	return desc->rmp_entry + segment_index;
 }
 
 static int get_rmpentry(u64 pfn, struct rmpread *entry)
-- 
2.46.2

[PATCH v4 7/8] x86/sev: Add full support for a segmented RMP table

[Tom Lendacky]

A segmented RMP table allows for improved locality of reference between
the memory protected by the RMP and the RMP entries themselves.

Add support to detect and initialize a segmented RMP table with multiple
segments as configured by the system BIOS. While the RMPREAD instruction
will be used to read an RMP entry in a segmented RMP, initialization and
debugging capabilities will require the mapping of the segments.

The RMP_CFG MSR indicates if segmented RMP support is enabled and, if
enabled, the amount of memory that an RMP segment covers. When segmented
RMP support is enabled, the RMP_BASE MSR points to the start of the RMP
bookkeeping area, which is 16K in size. The RMP Segment Table (RST) is
located immediately after the bookkeeping area and is 4K in size. The RST
contains up to 512 8-byte entries that identify the location of the RMP
segment and amount of memory mapped by the segment (which must be less
than or equal to the configured segment size). The physical address that
is covered by a segment is based on the segment size and the index of the
segment in the RST. The RMP entry for a physical address is based on the
offset within the segment.

  For example, if the segment size is 64GB (0x1000000000 or 1 << 36), then
  physical address 0x9000800000 is RST entry 9 (0x9000800000 >> 36) and
  RST entry 9 covers physical memory 0x9000000000 to 0x9FFFFFFFFF.

  The RMP entry index within the RMP segment is the physical address
  AND-ed with the segment mask, 64GB - 1 (0xFFFFFFFFF), and then
  right-shifted 12 bits or PHYS_PFN(0x9000800000 & 0xFFFFFFFFF), which
  is 0x800.

CPUID 0x80000025_EBX[9:0] describes the number of RMP segments that can
be cached by the hardware. Additionally, if CPUID 0x80000025_EBX[10] is
set, then the number of actual RMP segments defined cannot exceed the
number of RMP segments that can be cached and can be used as a maximum
RST index.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/cpufeatures.h |   1 +
 arch/x86/include/asm/msr-index.h   |   8 +-
 arch/x86/virt/svm/sev.c            | 251 ++++++++++++++++++++++++++---
 3 files changed, 236 insertions(+), 24 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 89c1308cdf54..bf2485bbe184 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -449,6 +449,7 @@
 #define X86_FEATURE_SME_COHERENT	(19*32+10) /* AMD hardware-enforced cache coherency */
 #define X86_FEATURE_DEBUG_SWAP		(19*32+14) /* "debug_swap" AMD SEV-ES full debug state swap support */
 #define X86_FEATURE_RMPREAD		(19*32+21) /* RMPREAD instruction */
+#define X86_FEATURE_SEGMENTED_RMP	(19*32+23) /* Segmented RMP support */
 #define X86_FEATURE_SVSM		(19*32+28) /* "svsm" SVSM present */
 
 /* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3ae84c3b8e6d..3f3e2bc99162 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -644,6 +644,7 @@
 #define MSR_AMD64_IBS_REG_COUNT_MAX	8 /* includes MSR_AMD64_IBSBRTARGET */
 #define MSR_AMD64_SVM_AVIC_DOORBELL	0xc001011b
 #define MSR_AMD64_VM_PAGE_FLUSH		0xc001011e
+#define MSR_AMD64_VIRT_SPEC_CTRL	0xc001011f
 #define MSR_AMD64_SEV_ES_GHCB		0xc0010130
 #define MSR_AMD64_SEV			0xc0010131
 #define MSR_AMD64_SEV_ENABLED_BIT	0
@@ -682,11 +683,12 @@
 #define MSR_AMD64_SNP_SMT_PROT		BIT_ULL(MSR_AMD64_SNP_SMT_PROT_BIT)
 #define MSR_AMD64_SNP_RESV_BIT		18
 #define MSR_AMD64_SNP_RESERVED_MASK	GENMASK_ULL(63, MSR_AMD64_SNP_RESV_BIT)
-
-#define MSR_AMD64_VIRT_SPEC_CTRL	0xc001011f
-
 #define MSR_AMD64_RMP_BASE		0xc0010132
 #define MSR_AMD64_RMP_END		0xc0010133
+#define MSR_AMD64_RMP_CFG		0xc0010136
+#define MSR_AMD64_SEG_RMP_ENABLED_BIT	0
+#define MSR_AMD64_SEG_RMP_ENABLED	BIT_ULL(MSR_AMD64_SEG_RMP_ENABLED_BIT)
+#define MSR_AMD64_RMP_SEGMENT_SHIFT(x)	(((x) & GENMASK_ULL(13, 8)) >> 8)
 
 #define MSR_SVSM_CAA			0xc001f000
 
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 043b2582e10e..f4f801f1c328 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -97,6 +97,10 @@ struct rmp_segment_desc {
  *     a specific portion of memory. There can be up to 512 8-byte entries,
  *     one pages worth.
  */
+#define RST_ENTRY_MAPPED_SIZE(x)	((x) & GENMASK_ULL(19, 0))
+#define RST_ENTRY_SEGMENT_BASE(x)	((x) & GENMASK_ULL(51, 20))
+
+#define RMP_SEGMENT_TABLE_SIZE	SZ_4K
 static struct rmp_segment_desc **rmp_segment_table __ro_after_init;
 static unsigned int rst_max_index __ro_after_init = 512;
 
@@ -107,6 +111,9 @@ static u64 rmp_segment_coverage_mask;
 #define RST_ENTRY_INDEX(x)	((x) >> rmp_segment_coverage_shift)
 #define RMP_ENTRY_INDEX(x)	((u64)(PHYS_PFN((x) & rmp_segment_coverage_mask)))
 
+static u64 rmp_cfg;
+#define RMP_IS_SEGMENTED(x)	((x) & MSR_AMD64_SEG_RMP_ENABLED)
+
 /* Mask to apply to a PFN to get the first PFN of a 2MB page */
 #define PFN_PMD_MASK	GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)
 
@@ -196,7 +203,49 @@ static void __init __snp_fixup_e820_tables(u64 pa)
 void __init snp_fixup_e820_tables(void)
 {
 	__snp_fixup_e820_tables(probed_rmp_base);
-	__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
+
+	if (RMP_IS_SEGMENTED(rmp_cfg)) {
+		u64 pa, *rst, size, mapped_size;
+		unsigned int i;
+
+		pa = probed_rmp_base;
+		pa += RMPTABLE_CPU_BOOKKEEPING_SZ;
+		pa += RMP_SEGMENT_TABLE_SIZE;
+		__snp_fixup_e820_tables(pa);
+
+		pa -= RMP_SEGMENT_TABLE_SIZE;
+		rst = early_memremap(pa, RMP_SEGMENT_TABLE_SIZE);
+		if (!rst)
+			return;
+
+		for (i = 0; i < rst_max_index; i++) {
+			pa = RST_ENTRY_SEGMENT_BASE(rst[i]);
+			mapped_size = RST_ENTRY_MAPPED_SIZE(rst[i]);
+			if (!mapped_size)
+				continue;
+
+			__snp_fixup_e820_tables(pa);
+
+			/*
+			 * Mapped size in GB. Mapped size is allowed to exceed
+			 * the segment coverage size, but gets reduced to the
+			 * segment coverage size.
+			 */
+			mapped_size <<= 30;
+			if (mapped_size > rmp_segment_coverage_size)
+				mapped_size = rmp_segment_coverage_size;
+
+			/* Calculate the RMP segment size (16 bytes/page mapped) */
+			size = PHYS_PFN(mapped_size);
+			size <<= 4;
+
+			__snp_fixup_e820_tables(pa + size);
+		}
+
+		early_memunmap(rst, RMP_SEGMENT_TABLE_SIZE);
+	} else {
+		__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
+	}
 }
 
 static bool __init init_rmptable_bookkeeping(void)
@@ -302,29 +351,17 @@ static bool __init alloc_rmp_segment_table(void)
 	return true;
 }
 
-/*
- * Do the necessary preparations which are verified by the firmware as
- * described in the SNP_INIT_EX firmware command description in the SNP
- * firmware ABI spec.
- */
-static int __init snp_rmptable_init(void)
+static bool __init contiguous_rmptable_setup(void)
 {
-	u64 max_rmp_pfn, calc_rmp_sz, rmptable_segment, rmptable_size, rmp_end, val;
-	unsigned int i;
-
-	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
-		return 0;
-
-	if (!amd_iommu_snp_en)
-		goto nosnp;
+	u64 max_rmp_pfn, calc_rmp_sz, rmptable_segment, rmptable_size, rmp_end;
 
 	if (!probed_rmp_size)
-		goto nosnp;
+		return false;
 
 	rmp_end = probed_rmp_base + probed_rmp_size - 1;
 
 	/*
-	 * Calculate the amount the memory that must be reserved by the BIOS to
+	 * Calculate the amount of memory that must be reserved by the BIOS to
 	 * address the whole RAM, including the bookkeeping area. The RMP itself
 	 * must also be covered.
 	 */
@@ -336,11 +373,11 @@ static int __init snp_rmptable_init(void)
 	if (calc_rmp_sz > probed_rmp_size) {
 		pr_err("Memory reserved for the RMP table does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
 		       calc_rmp_sz, probed_rmp_size);
-		goto nosnp;
+		return false;
 	}
 
 	if (!alloc_rmp_segment_table())
-		goto nosnp;
+		return false;
 
 	/* Map only the RMP entries */
 	rmptable_segment = probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ;
@@ -348,9 +385,127 @@ static int __init snp_rmptable_init(void)
 
 	if (!alloc_rmp_segment_desc(rmptable_segment, rmptable_size, 0)) {
 		free_rmp_segment_table();
-		goto nosnp;
+		return false;
 	}
 
+	return true;
+}
+
+static bool __init segmented_rmptable_setup(void)
+{
+	u64 rst_pa, *rst, pa, ram_pa_end, ram_pa_max;
+	unsigned int i, max_index;
+
+	if (!probed_rmp_base)
+		return false;
+
+	if (!alloc_rmp_segment_table())
+		return false;
+
+	/* Map the RMP Segment Table */
+	rst_pa = probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ;
+	rst = memremap(rst_pa, RMP_SEGMENT_TABLE_SIZE, MEMREMAP_WB);
+	if (!rst) {
+		pr_err("Failed to map RMP segment table addr %#llx\n", rst_pa);
+		goto e_free;
+	}
+
+	/* Get the address for the end of system RAM */
+	ram_pa_max = max_pfn << PAGE_SHIFT;
+
+	/* Process each RMP segment */
+	max_index = 0;
+	ram_pa_end = 0;
+	for (i = 0; i < rst_max_index; i++) {
+		u64 rmp_segment, rmp_size, mapped_size;
+
+		mapped_size = RST_ENTRY_MAPPED_SIZE(rst[i]);
+		if (!mapped_size)
+			continue;
+
+		max_index = i;
+
+		/*
+		 * Mapped size in GB. Mapped size is allowed to exceed the
+		 * segment coverage size, but gets reduced to the segment
+		 * coverage size.
+		 */
+		mapped_size <<= 30;
+		if (mapped_size > rmp_segment_coverage_size) {
+			pr_info("RMP segment %u mapped size (0x%llx) reduced to 0x%llx\n",
+				i, mapped_size, rmp_segment_coverage_size);
+			mapped_size = rmp_segment_coverage_size;
+		}
+
+		rmp_segment = RST_ENTRY_SEGMENT_BASE(rst[i]);
+
+		/* Calculate the RMP segment size (16 bytes/page mapped) */
+		rmp_size = PHYS_PFN(mapped_size);
+		rmp_size <<= 4;
+
+		pa = (u64)i << rmp_segment_coverage_shift;
+
+		/*
+		 * Some segments may be for MMIO mapped above system RAM. These
+		 * segments are used for Trusted I/O.
+		 */
+		if (pa < ram_pa_max)
+			ram_pa_end = pa + mapped_size;
+
+		if (!alloc_rmp_segment_desc(rmp_segment, rmp_size, pa))
+			goto e_unmap;
+
+		pr_info("RMP segment %u physical address [%#llx - %#llx] covering [%#llx - %#llx]\n",
+			i, rmp_segment, rmp_segment + rmp_size - 1, pa, pa + mapped_size - 1);
+	}
+
+	if (ram_pa_max > ram_pa_end) {
+		pr_err("Segmented RMP does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
+		       ram_pa_max, ram_pa_end);
+		goto e_unmap;
+	}
+
+	/* Adjust the maximum index based on the found segments */
+	rst_max_index = max_index + 1;
+
+	memunmap(rst);
+
+	return true;
+
+e_unmap:
+	memunmap(rst);
+
+e_free:
+	free_rmp_segment_table();
+
+	return false;
+}
+
+static bool __init rmptable_setup(void)
+{
+	return RMP_IS_SEGMENTED(rmp_cfg) ? segmented_rmptable_setup()
+					 : contiguous_rmptable_setup();
+}
+
+/*
+ * Do the necessary preparations which are verified by the firmware as
+ * described in the SNP_INIT_EX firmware command description in the SNP
+ * firmware ABI spec.
+ */
+static int __init snp_rmptable_init(void)
+{
+	unsigned int i;
+	u64 val;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return 0;
+
+	if (!amd_iommu_snp_en)
+		goto nosnp;
+
+	if (!rmptable_setup())
+		goto nosnp;
+
 	/*
 	 * Check if SEV-SNP is already enabled, this can happen in case of
 	 * kexec boot.
@@ -418,7 +573,7 @@ static void set_rmp_segment_info(unsigned int segment_shift)
 
 #define RMP_ADDR_MASK GENMASK_ULL(51, 13)
 
-bool snp_probe_rmptable_info(void)
+static bool probe_contiguous_rmptable_info(void)
 {
 	u64 rmp_sz, rmp_base, rmp_end;
 
@@ -451,6 +606,60 @@ bool snp_probe_rmptable_info(void)
 	return true;
 }
 
+static bool probe_segmented_rmptable_info(void)
+{
+	unsigned int eax, ebx, segment_shift, segment_shift_min, segment_shift_max;
+	u64 rmp_base, rmp_end;
+
+	rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
+	rdmsrl(MSR_AMD64_RMP_END, rmp_end);
+
+	if (!(rmp_base & RMP_ADDR_MASK)) {
+		pr_err("Memory for the RMP table has not been reserved by BIOS\n");
+		return false;
+	}
+
+	WARN_ONCE(rmp_end & RMP_ADDR_MASK,
+		  "Segmented RMP enabled but RMP_END MSR is non-zero\n");
+
+	/* Obtain the min and max supported RMP segment size */
+	eax = cpuid_eax(0x80000025);
+	segment_shift_min = eax & GENMASK(5, 0);
+	segment_shift_max = (eax & GENMASK(11, 6)) >> 6;
+
+	/* Verify the segment size is within the supported limits */
+	segment_shift = MSR_AMD64_RMP_SEGMENT_SHIFT(rmp_cfg);
+	if (segment_shift > segment_shift_max || segment_shift < segment_shift_min) {
+		pr_err("RMP segment size (%u) is not within advertised bounds (min=%u, max=%u)\n",
+		       segment_shift, segment_shift_min, segment_shift_max);
+		return false;
+	}
+
+	/* Override the max supported RST index if a hardware limit exists */
+	ebx = cpuid_ebx(0x80000025);
+	if (ebx & BIT(10))
+		rst_max_index = ebx & GENMASK(9, 0);
+
+	set_rmp_segment_info(segment_shift);
+
+	probed_rmp_base = rmp_base;
+	probed_rmp_size = 0;
+
+	pr_info("Segmented RMP base table physical range [0x%016llx - 0x%016llx]\n",
+		rmp_base, rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ + RMP_SEGMENT_TABLE_SIZE);
+
+	return true;
+}
+
+bool snp_probe_rmptable_info(void)
+{
+	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP))
+		rdmsrl(MSR_AMD64_RMP_CFG, rmp_cfg);
+
+	return RMP_IS_SEGMENTED(rmp_cfg) ? probe_segmented_rmptable_info()
+					 : probe_contiguous_rmptable_info();
+}
+
 static struct rmpentry *__get_rmpentry(u64 pfn)
 {
 	struct rmp_segment_desc *desc;
-- 
2.46.2

[PATCH v4 8/8] x86/sev/docs: Document the SNP Reverse Map Table (RMP)

[Tom Lendacky]

Update the AMD memory encryption documentation to include information on
the Reverse Map Table (RMP) and the two table formats.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 .../arch/x86/amd-memory-encryption.rst        | 118 ++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/Documentation/arch/x86/amd-memory-encryption.rst b/Documentation/arch/x86/amd-memory-encryption.rst
index 6df3264f23b9..bd840df708ea 100644
--- a/Documentation/arch/x86/amd-memory-encryption.rst
+++ b/Documentation/arch/x86/amd-memory-encryption.rst
@@ -130,8 +130,126 @@ SNP feature support.
 
 More details in AMD64 APM[1] Vol 2: 15.34.10 SEV_STATUS MSR
 
+Reverse Map Table (RMP)
+=======================
+
+The RMP is a structure in system memory that is used to ensure a one-to-one
+mapping between system physical addresses and guest physical addresses. Each
+page of memory that is potentially assignable to guests has one entry within
+the RMP.
+
+The RMP table can be either contiguous in memory or a collection of segments
+in memory.
+
+Contiguous RMP
+--------------
+
+Support for this form of the RMP is present when support for SEV-SNP is
+present, which can be determined using the CPUID instruction::
+
+	0x8000001f[eax]:
+		Bit[4] indicates support for SEV-SNP
+
+The location of the RMP is identified to the hardware through two MSRs::
+
+        0xc0010132 (RMP_BASE):
+                System physical address of the first byte of the RMP
+
+        0xc0010133 (RMP_END):
+                System physical address of the last byte of the RMP
+
+Hardware requires that RMP_BASE and (RPM_END + 1) be 8KB aligned, but SEV
+firmware increases the alignment requirement to require a 1MB alignment.
+
+The RMP consists of a 16KB region used for processor bookkeeping followed
+by the RMP entries, which are 16 bytes in size. The size of the RMP
+determines the range of physical memory that the hypervisor can assign to
+SEV-SNP guests. The RMP covers the system physical address from::
+
+        0 to ((RMP_END + 1 - RMP_BASE - 16KB) / 16B) x 4KB.
+
+The current Linux support relies on BIOS to allocate/reserve the memory for
+the RMP and to set RMP_BASE and RMP_END appropriately. Linux uses the MSR
+values to locate the RMP and determine the size of the RMP. The RMP must
+cover all of system memory in order for Linux to enable SEV-SNP.
+
+Segmented RMP
+-------------
+
+Segmented RMP support is a new way of representing the layout of an RMP.
+Initial RMP support required the RMP table to be contiguous in memory.
+RMP accesses from a NUMA node on which the RMP doesn't reside
+can take longer than accesses from a NUMA node on which the RMP resides.
+Segmented RMP support allows the RMP entries to be located on the same
+node as the memory the RMP is covering, potentially reducing latency
+associated with accessing an RMP entry associated with the memory. Each
+RMP segment covers a specific range of system physical addresses.
+
+Support for this form of the RMP can be determined using the CPUID
+instruction::
+
+        0x8000001f[eax]:
+                Bit[23] indicates support for segmented RMP
+
+If supported, segmented RMP attributes can be found using the CPUID
+instruction::
+
+        0x80000025[eax]:
+                Bits[5:0]  minimum supported RMP segment size
+                Bits[11:6] maximum supported RMP segment size
+
+        0x80000025[ebx]:
+                Bits[9:0]  number of cacheable RMP segment definitions
+                Bit[10]    indicates if the number of cacheable RMP segments
+                           is a hard limit
+
+To enable a segmented RMP, a new MSR is available::
+
+        0xc0010136 (RMP_CFG):
+                Bit[0]     indicates if segmented RMP is enabled
+                Bits[13:8] contains the size of memory covered by an RMP
+                           segment (expressed as a power of 2)
+
+The RMP segment size defined in the RMP_CFG MSR applies to all segments
+of the RMP. Therefore each RMP segment covers a specific range of system
+physical addresses. For example, if the RMP_CFG MSR value is 0x2401, then
+the RMP segment coverage value is 0x24 => 36, meaning the size of memory
+covered by an RMP segment is 64GB (1 << 36). So the first RMP segment
+covers physical addresses from 0 to 0xF_FFFF_FFFF, the second RMP segment
+covers physical addresses from 0x10_0000_0000 to 0x1F_FFFF_FFFF, etc.
+
+When a segmented RMP is enabled, RMP_BASE points to the RMP bookkeeping
+area as it does today (16K in size). However, instead of RMP entries
+beginning immediately after the bookkeeping area, there is a 4K RMP
+segment table (RST). Each entry in the RST is 8-bytes in size and represents
+an RMP segment::
+
+        Bits[19:0]  mapped size (in GB)
+                    The mapped size can be less than the defined segment size.
+                    A value of zero, indicates that no RMP exists for the range
+                    of system physical addresses associated with this segment.
+        Bits[51:20] segment physical address
+                    This address is left shift 20-bits (or just masked when
+                    read) to form the physical address of the segment (1MB
+                    alignment).
+
+The RST can hold 512 segment entries but can be limited in size to the number
+of cacheable RMP segments (CPUID 0x80000025_EBX[9:0]) if the number of cacheable
+RMP segments is a hard limit (CPUID 0x80000025_EBX[10]).
+
+The current Linux support relies on BIOS to allocate/reserve the memory for
+the segmented RMP (the bookkeeping area, RST, and all segments), build the RST
+and to set RMP_BASE, RMP_END, and RMP_CFG appropriately. Linux uses the MSR
+values to locate the RMP and determine the size and location of the RMP
+segments. The RMP must cover all of system memory in order for Linux to enable
+SEV-SNP.
+
+More details in the AMD64 APM Vol 2, section "15.36.3 Reverse Map Table",
+docID: 24593.
+
 Secure VM Service Module (SVSM)
 ===============================
+
 SNP provides a feature called Virtual Machine Privilege Levels (VMPL) which
 defines four privilege levels at which guest software can run. The most
 privileged level is 0 and numerically higher numbers have lesser privileges.
-- 
2.46.2

Re: [PATCH v4 0/8] Provide support for RMPREAD and a segmented RMP

[Neeraj Upadhyay]

On 10/24/2024 12:11 AM, Tom Lendacky wrote:
> This series adds SEV-SNP support for a new instruction to read an RMP
> entry and for a segmented RMP table.
> 
> The RMPREAD instruction is used to return information related to an RMP
> entry in an architecturally defined format.
> 
> RMPREAD support is detected via CPUID 0x8000001f_EAX[21].
> 
> Segmented RMP support is a new way of representing the layout of an RMP
> table. Initial RMP table support required the RMP table to be contiguous
> in memory. RMP accesses from a NUMA node on which the RMP doesn't reside
> can take longer than accesses from a NUMA node on which the RMP resides.
> Segmented RMP support allows the RMP entries to be located on the same
> node as the memory the RMP is covering, potentially reducing latency
> associated with accessing an RMP entry associated with the memory. Each
> RMP segment covers a specific range of system physical addresses.
> 
> Segmented RMP support is detected and established via CPUID and MSRs.
> 
> CPUID:
>   - 0x8000001f_EAX[23]
>     - Indicates support for segmented RMP
> 
>   - 0x80000025_EAX
>     - [5:0]   : Minimum supported RMP segment size
>     - [11:6]  : Maximum supported RMP segment size
> 
>   - 0x80000025_EBX
>     - [9:0]   : Number of cacheable RMP segment definitions
>     - [10]    : Indicates if the number of cacheable RMP segments is
>                 a hard limit
> 
> MSR:
>   - 0xc0010132 (RMP_BASE)
>     - Is identical to current RMP support
> 
>   - 0xc0010133 (RMP_END)
>     - Should be in reset state if segmented RMP support is active
> 
>       For kernels that do not support segmented RMP, being in reset
>       state allows the kernel to disable SNP support if the non-segmented
>       RMP has not been allocated.
> 
>   - 0xc0010136 (RMP_CFG)
>     - [0]    : Indicates if segmented RMP is enabled
>     - [13:8] : Contains the size of memory covered by an RMP segment
>                (expressed as a power of 2)
> 
> The RMP segment size defined in the RMP_CFG MSR applies to all segments
> of the RMP. Therefore each RMP segment covers a specific range of system
> physical addresses. For example, if the RMP_CFG MSR value is 0x2401, then
> the RMP segment coverage value is 0x24 => 36, meaning the size of memory
> covered by an RMP segment is 64GB (1 << 36). So the first RMP segment
> covers physical addresses from 0 to 0xF_FFFF_FFFF, the second RMP segment
> covers physical addresses from 0x10_0000_0000 to 0x1F_FFFF_FFFF, etc.
> 
> When a segmented RMP is enabled, RMP_BASE points to the RMP bookkeeping
> area as it does today (16K in size). However, instead of RMP entries
> beginning immediately after the bookkeeping area, there is a 4K RMP
> segment table. Each entry in the table is 8-bytes in size:
> 
>   - [19:0]  : Mapped size (in GB)
>               The mapped size can be less than the defined segment size.
>               A value of zero, indicates that no RMP exists for the range
>               of system physical addresses associated with this segment.
>     [51:20] : Segment physical address
>               This address is left shift 20-bits (or just masked when
>               read) to form the physical address of the segment (1MB
>               alignment).
> 
> The series is based off of and tested against the tip tree:
>   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master
> 
>   94559bac4d40 ("Merge branch into tip/master: 'x86/sev'")
> 
> ---
> 

For the series:

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>


- Neeraj

Re: [PATCH v4 0/8] Provide support for RMPREAD and a segmented RMP

[Nikunj A. Dadhania]

On 10/24/2024 12:11 AM, Tom Lendacky wrote:
> This series adds SEV-SNP support for a new instruction to read an RMP
> entry and for a segmented RMP table.
> 
> The RMPREAD instruction is used to return information related to an RMP
> entry in an architecturally defined format.
> 
> RMPREAD support is detected via CPUID 0x8000001f_EAX[21].
> 
> Segmented RMP support is a new way of representing the layout of an RMP
> table. Initial RMP table support required the RMP table to be contiguous
> in memory. RMP accesses from a NUMA node on which the RMP doesn't reside
> can take longer than accesses from a NUMA node on which the RMP resides.
> Segmented RMP support allows the RMP entries to be located on the same
> node as the memory the RMP is covering, potentially reducing latency
> associated with accessing an RMP entry associated with the memory. Each
> RMP segment covers a specific range of system physical addresses.
> 
> Segmented RMP support is detected and established via CPUID and MSRs.
> 
> CPUID:
>   - 0x8000001f_EAX[23]
>     - Indicates support for segmented RMP
> 
>   - 0x80000025_EAX
>     - [5:0]   : Minimum supported RMP segment size
>     - [11:6]  : Maximum supported RMP segment size
> 
>   - 0x80000025_EBX
>     - [9:0]   : Number of cacheable RMP segment definitions
>     - [10]    : Indicates if the number of cacheable RMP segments is
>                 a hard limit
> 
> MSR:
>   - 0xc0010132 (RMP_BASE)
>     - Is identical to current RMP support
> 
>   - 0xc0010133 (RMP_END)
>     - Should be in reset state if segmented RMP support is active
> 
>       For kernels that do not support segmented RMP, being in reset
>       state allows the kernel to disable SNP support if the non-segmented
>       RMP has not been allocated.
> 
>   - 0xc0010136 (RMP_CFG)
>     - [0]    : Indicates if segmented RMP is enabled
>     - [13:8] : Contains the size of memory covered by an RMP segment
>                (expressed as a power of 2)
> 
> The RMP segment size defined in the RMP_CFG MSR applies to all segments
> of the RMP. Therefore each RMP segment covers a specific range of system
> physical addresses. For example, if the RMP_CFG MSR value is 0x2401, then
> the RMP segment coverage value is 0x24 => 36, meaning the size of memory
> covered by an RMP segment is 64GB (1 << 36). So the first RMP segment
> covers physical addresses from 0 to 0xF_FFFF_FFFF, the second RMP segment
> covers physical addresses from 0x10_0000_0000 to 0x1F_FFFF_FFFF, etc.
> 
> When a segmented RMP is enabled, RMP_BASE points to the RMP bookkeeping
> area as it does today (16K in size). However, instead of RMP entries
> beginning immediately after the bookkeeping area, there is a 4K RMP
> segment table. Each entry in the table is 8-bytes in size:
> 
>   - [19:0]  : Mapped size (in GB)
>               The mapped size can be less than the defined segment size.
>               A value of zero, indicates that no RMP exists for the range
>               of system physical addresses associated with this segment.
>     [51:20] : Segment physical address
>               This address is left shift 20-bits (or just masked when
>               read) to form the physical address of the segment (1MB
>               alignment).
> 
> The series is based off of and tested against the tip tree:
>   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master
> 
>   94559bac4d40 ("Merge branch into tip/master: 'x86/sev'")
> 
> ---
> 
> Changes in v4:
> - Change the structure name of the newly introduced RMPREAD state data
>   to rmpread, to avoid churn around the renaming of the old rmpentry
>   structure.
> - Change the fam19h check to be explicit ZEN3/ZEN4 checks
> - Unify the use of u64 for RMP-related values instead of using a mix of
>   u64 and unsigned long.
> - Fix the RMP segment end calculation in __snp_fixup_e820_tables().
> - Minor message cleanups and code simplifications.
> 
> Changes in v3:
> - Added RMP documentation
> 
> Changes in v2:
> - Remove the self-describing check. The SEV firmware will ensure that
>   all RMP segments are covered by RMP entries.
> - Do not include RMP segments above maximum detected RAM address (64-bit
>   MMIO) in the system RAM coverage check.
> - Adjust new CPUID feature entries to match the change to how they are
>   or are not presented to userspace.
> 
> 
> Tom Lendacky (8):
>   x86/sev: Prepare for using the RMPREAD instruction to access the RMP
>   x86/sev: Add support for the RMPREAD instruction
>   x86/sev: Require the RMPREAD instruction after Zen4
>   x86/sev: Move the SNP probe routine out of the way
>   x86/sev: Map only the RMP table entries instead of the full RMP range
>   x86/sev: Treat the contiguous RMP table as a single RMP segment
>   x86/sev: Add full support for a segmented RMP table
>   x86/sev/docs: Document the SNP Reverse Map Table (RMP)
> 
>  .../arch/x86/amd-memory-encryption.rst        | 118 ++++
>  arch/x86/include/asm/cpufeatures.h            |   2 +
>  arch/x86/include/asm/msr-index.h              |   8 +-
>  arch/x86/kernel/cpu/amd.c                     |   9 +-
>  arch/x86/virt/svm/sev.c                       | 632 +++++++++++++++---
>  5 files changed, 675 insertions(+), 94 deletions(-)
> 

For the series:

Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>

Regards,
Nikunj

Re: [PATCH v4 8/8] x86/sev/docs: Document the SNP Reverse Map Table (RMP)

[Kalra, Ashish]

On 10/23/2024 1:42 PM, Tom Lendacky wrote:
> Update the AMD memory encryption documentation to include information on
> the Reverse Map Table (RMP) and the two table formats.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  .../arch/x86/amd-memory-encryption.rst        | 118 ++++++++++++++++++
>  1 file changed, 118 insertions(+)
> 
> diff --git a/Documentation/arch/x86/amd-memory-encryption.rst b/Documentation/arch/x86/amd-memory-encryption.rst
> index 6df3264f23b9..bd840df708ea 100644
> --- a/Documentation/arch/x86/amd-memory-encryption.rst
> +++ b/Documentation/arch/x86/amd-memory-encryption.rst
> @@ -130,8 +130,126 @@ SNP feature support.
>  
>  More details in AMD64 APM[1] Vol 2: 15.34.10 SEV_STATUS MSR
>  
> +Reverse Map Table (RMP)
> +=======================
> +
> +The RMP is a structure in system memory that is used to ensure a one-to-one
> +mapping between system physical addresses and guest physical addresses. Each
> +page of memory that is potentially assignable to guests has one entry within
> +the RMP.
> +
> +The RMP table can be either contiguous in memory or a collection of segments
> +in memory.
> +
> +Contiguous RMP
> +--------------
> +
> +Support for this form of the RMP is present when support for SEV-SNP is
> +present, which can be determined using the CPUID instruction::
> +
> +	0x8000001f[eax]:
> +		Bit[4] indicates support for SEV-SNP
> +
> +The location of the RMP is identified to the hardware through two MSRs::
> +
> +        0xc0010132 (RMP_BASE):
> +                System physical address of the first byte of the RMP
> +
> +        0xc0010133 (RMP_END):
> +                System physical address of the last byte of the RMP
> +
> +Hardware requires that RMP_BASE and (RPM_END + 1) be 8KB aligned, but SEV
> +firmware increases the alignment requirement to require a 1MB alignment.
> +
> +The RMP consists of a 16KB region used for processor bookkeeping followed
> +by the RMP entries, which are 16 bytes in size. The size of the RMP
> +determines the range of physical memory that the hypervisor can assign to
> +SEV-SNP guests. The RMP covers the system physical address from::
> +
> +        0 to ((RMP_END + 1 - RMP_BASE - 16KB) / 16B) x 4KB.
> +
> +The current Linux support relies on BIOS to allocate/reserve the memory for
> +the RMP and to set RMP_BASE and RMP_END appropriately. Linux uses the MSR
> +values to locate the RMP and determine the size of the RMP. The RMP must
> +cover all of system memory in order for Linux to enable SEV-SNP.
> +
> +Segmented RMP
> +-------------
> +
> +Segmented RMP support is a new way of representing the layout of an RMP.
> +Initial RMP support required the RMP table to be contiguous in memory.
> +RMP accesses from a NUMA node on which the RMP doesn't reside
> +can take longer than accesses from a NUMA node on which the RMP resides.
> +Segmented RMP support allows the RMP entries to be located on the same
> +node as the memory the RMP is covering, potentially reducing latency
> +associated with accessing an RMP entry associated with the memory. Each
> +RMP segment covers a specific range of system physical addresses.
> +
> +Support for this form of the RMP can be determined using the CPUID
> +instruction::
> +
> +        0x8000001f[eax]:
> +                Bit[23] indicates support for segmented RMP
> +
> +If supported, segmented RMP attributes can be found using the CPUID
> +instruction::
> +
> +        0x80000025[eax]:
> +                Bits[5:0]  minimum supported RMP segment size
> +                Bits[11:6] maximum supported RMP segment size
> +
> +        0x80000025[ebx]:
> +                Bits[9:0]  number of cacheable RMP segment definitions
> +                Bit[10]    indicates if the number of cacheable RMP segments
> +                           is a hard limit
> +

Some more details on cacheable RMP segments on why are they supported, platform/processor specific ? 

> +To enable a segmented RMP, a new MSR is available::
> +
> +        0xc0010136 (RMP_CFG):
> +                Bit[0]     indicates if segmented RMP is enabled
> +                Bits[13:8] contains the size of memory covered by an RMP
> +                           segment (expressed as a power of 2)
> +
> +The RMP segment size defined in the RMP_CFG MSR applies to all segments
> +of the RMP. Therefore each RMP segment covers a specific range of system
> +physical addresses. For example, if the RMP_CFG MSR value is 0x2401, then
> +the RMP segment coverage value is 0x24 => 36, meaning the size of memory
> +covered by an RMP segment is 64GB (1 << 36). So the first RMP segment
> +covers physical addresses from 0 to 0xF_FFFF_FFFF, the second RMP segment
> +covers physical addresses from 0x10_0000_0000 to 0x1F_FFFF_FFFF, etc.
> +
> +When a segmented RMP is enabled, RMP_BASE points to the RMP bookkeeping
> +area as it does today (16K in size). However, instead of RMP entries
> +beginning immediately after the bookkeeping area, there is a 4K RMP
> +segment table (RST). Each entry in the RST is 8-bytes in size and represents
> +an RMP segment::
> +
> +        Bits[19:0]  mapped size (in GB)
> +                    The mapped size can be less than the defined segment size.
> +                    A value of zero, indicates that no RMP exists for the range
> +                    of system physical addresses associated with this segment.
> +        Bits[51:20] segment physical address
> +                    This address is left shift 20-bits (or just masked when
> +                    read) to form the physical address of the segment (1MB
> +                    alignment).
> +
> +The RST can hold 512 segment entries but can be limited in size to the number
> +of cacheable RMP segments (CPUID 0x80000025_EBX[9:0]) if the number of cacheable
> +RMP segments is a hard limit (CPUID 0x80000025_EBX[10]).
> +
> +The current Linux support relies on BIOS to allocate/reserve the memory for
> +the segmented RMP (the bookkeeping area, RST, and all segments), build the RST
> +and to set RMP_BASE, RMP_END, and RMP_CFG appropriately. Linux uses the MSR
> +values to locate the RMP and determine the size and location of the RMP
> +segments. The RMP must cover all of system memory in order for Linux to enable
> +SEV-SNP.
> +
> +More details in the AMD64 APM Vol 2, section "15.36.3 Reverse Map Table",
> +docID: 24593.

The document does not cover Segmented RMP specifics, is there any other reference to a document
containing Segmented RMP details ?

Thanks, 
Ashish

> +
>  Secure VM Service Module (SVSM)
>  ===============================
> +
>  SNP provides a feature called Virtual Machine Privilege Levels (VMPL) which
>  defines four privilege levels at which guest software can run. The most
>  privileged level is 0 and numerically higher numbers have lesser privileges.

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Kalra, Ashish]

, 
On 10/23/2024 1:41 PM, Tom Lendacky wrote:
> The RMPREAD instruction returns an architecture defined format of an
> RMP entry. This is the preferred method for examining RMP entries.
> 
> In preparation for using the RMPREAD instruction, convert the existing
> code that directly accesses the RMP to map the raw RMP information into
> the architecture defined format.
> 
> RMPREAD output returns a status bit for the 2MB region status. If the
> input page address is 2MB aligned and any other pages within the 2MB
> region are assigned, then 2MB region status will be set to 1. Otherwise,
> the 2MB region status will be set to 0. For systems that do not support
> RMPREAD, calculating this value would require looping over all of the RMP
> table entries within that range until one is found with the assigned bit
> set. Since this bit is not defined in the current format, and so not used
> today, do not incur the overhead associated with calculating it.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/virt/svm/sev.c | 121 +++++++++++++++++++++++++++++-----------
>  1 file changed, 87 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 0ce17766c0e5..4d095affdb4d 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -30,6 +30,22 @@
>  #include <asm/cmdline.h>
>  #include <asm/iommu.h>
>  
> +/*
> + * The RMP entry format as returned by the RMPREAD instruction.
> + */
> +struct rmpread {
> +	u64 gpa;
> +	u8  assigned		:1,
> +	    rsvd1		:7;
> +	u8  pagesize		:1,
> +	    hpage_region_status	:1,
> +	    rsvd2		:6;
> +	u8  immutable		:1,
> +	    rsvd3		:7;
> +	u8  rsvd4;
> +	u32 asid;
> +} __packed;
> +
>  /*
>   * The RMP entry format is not architectural. The format is defined in PPR
>   * Family 19h Model 01h, Rev B1 processor.
> @@ -270,48 +286,77 @@ static int __init snp_rmptable_init(void)
>   */
>  device_initcall(snp_rmptable_init);
>  
> -static struct rmpentry *get_rmpentry(u64 pfn)
> +static struct rmpentry *__get_rmpentry(u64 pfn)
>  {
> -	if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
> -		return ERR_PTR(-EFAULT);
> -
> -	return &rmptable[pfn];
> -}
> -
> -static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
> -{
> -	struct rmpentry *large_entry, *entry;
> -
> -	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> +	if (!rmptable)
>  		return ERR_PTR(-ENODEV);
>  
> -	entry = get_rmpentry(pfn);
> -	if (IS_ERR(entry))
> -		return entry;
> +	if (unlikely(pfn > rmptable_max_pfn))

rmptable_max_pfn is initialized in patch#5, shouldn't this patch be moved after patch #5 ?

> +		return ERR_PTR(-EFAULT);
> +
> +	return rmptable + pfn;

Again, rmptable is initialized/setup in patch#5, similarly shouldn't this patch be moved
after patch #5 ?

Thanks,
Ashish

> +}
> +
> +static int get_rmpentry(u64 pfn, struct rmpread *entry)
> +{
> +	struct rmpentry *e;
> +
> +	e = __get_rmpentry(pfn);
> +	if (IS_ERR(e))
> +		return PTR_ERR(e);
> +
> +	/*
> +	 * Map the RMP table entry onto the RMPREAD output format.
> +	 * The 2MB region status indicator (hpage_region_status field) is not
> +	 * calculated, since the overhead could be significant and the field
> +	 * is not used.
> +	 */
> +	memset(entry, 0, sizeof(*entry));
> +	entry->gpa       = e->gpa << PAGE_SHIFT;
> +	entry->asid      = e->asid;
> +	entry->assigned  = e->assigned;
> +	entry->pagesize  = e->pagesize;
> +	entry->immutable = e->immutable;
> +
> +	return 0;
> +}
> +
> +static int __snp_lookup_rmpentry(u64 pfn, struct rmpread *entry, int *level)
> +{
> +	struct rmpread large_entry;
> +	int ret;
> +
> +	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> +		return -ENODEV;
> +
> +	ret = get_rmpentry(pfn, entry);
> +	if (ret)
> +		return ret;
>  
>  	/*
>  	 * Find the authoritative RMP entry for a PFN. This can be either a 4K
>  	 * RMP entry or a special large RMP entry that is authoritative for a
>  	 * whole 2M area.
>  	 */
> -	large_entry = get_rmpentry(pfn & PFN_PMD_MASK);
> -	if (IS_ERR(large_entry))
> -		return large_entry;
> +	ret = get_rmpentry(pfn & PFN_PMD_MASK, &large_entry);
> +	if (ret)
> +		return ret;
>  
> -	*level = RMP_TO_PG_LEVEL(large_entry->pagesize);
> +	*level = RMP_TO_PG_LEVEL(large_entry.pagesize);
>  
> -	return entry;
> +	return 0;
>  }
>  
>  int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
>  {
> -	struct rmpentry *e;
> +	struct rmpread rmpread;
> +	int ret;
>  
> -	e = __snp_lookup_rmpentry(pfn, level);
> -	if (IS_ERR(e))
> -		return PTR_ERR(e);
> +	ret = __snp_lookup_rmpentry(pfn, &rmpread, level);
> +	if (ret)
> +		return ret;
>  
> -	*assigned = !!e->assigned;
> +	*assigned = !!rmpread.assigned;
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
> @@ -324,18 +369,26 @@ EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
>   */
>  static void dump_rmpentry(u64 pfn)
>  {
> -	u64 pfn_i, pfn_end;
> +	struct rmpread rmpread;
>  	struct rmpentry *e;
> -	int level;
> +	u64 pfn_i, pfn_end;
> +	int level, ret;
>  
> -	e = __snp_lookup_rmpentry(pfn, &level);
> -	if (IS_ERR(e)) {
> -		pr_err("Failed to read RMP entry for PFN 0x%llx, error %ld\n",
> -		       pfn, PTR_ERR(e));
> +	ret = __snp_lookup_rmpentry(pfn, &rmpread, &level);
> +	if (ret) {
> +		pr_err("Failed to read RMP entry for PFN 0x%llx, error %d\n",
> +		       pfn, ret);
>  		return;
>  	}
>  
> -	if (e->assigned) {
> +	if (rmpread.assigned) {
> +		e = __get_rmpentry(pfn);
> +		if (IS_ERR(e)) {
> +			pr_err("Failed to read RMP contents for PFN 0x%llx, error %ld\n",
> +			       pfn, PTR_ERR(e));
> +			return;
> +		}
> +
>  		pr_info("PFN 0x%llx, RMP entry: [0x%016llx - 0x%016llx]\n",
>  			pfn, e->lo, e->hi);
>  		return;
> @@ -356,9 +409,9 @@ static void dump_rmpentry(u64 pfn)
>  		pfn, pfn_i, pfn_end);
>  
>  	while (pfn_i < pfn_end) {
> -		e = __snp_lookup_rmpentry(pfn_i, &level);
> +		e = __get_rmpentry(pfn_i);
>  		if (IS_ERR(e)) {
> -			pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",
> +			pr_err("Error %ld reading RMP contents for PFN 0x%llx\n",
>  			       PTR_ERR(e), pfn_i);
>  			pfn_i++;
>  			continue;

Re: [PATCH v4 2/8] x86/sev: Add support for the RMPREAD instruction

[Kalra, Ashish]

On 10/23/2024 1:41 PM, Tom Lendacky wrote:
> The RMPREAD instruction returns an architecture defined format of an
> RMP table entry. This is the preferred method for examining RMP entries.
> 
> The instruction is advertised in CPUID 0x8000001f_EAX[21]. Use this
> instruction when available.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/include/asm/cpufeatures.h |  1 +
>  arch/x86/virt/svm/sev.c            | 11 +++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 913fd3a7bac6..89c1308cdf54 10064
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -448,6 +448,7 @@
>  #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* Virtual TSC_AUX */
>  #define X86_FEATURE_SME_COHERENT	(19*32+10) /* AMD hardware-enforced cache coherency */
>  #define X86_FEATURE_DEBUG_SWAP		(19*32+14) /* "debug_swap" AMD SEV-ES full debug state swap support */
> +#define X86_FEATURE_RMPREAD		(19*32+21) /* RMPREAD instruction */
>  #define X86_FEATURE_SVSM		(19*32+28) /* "svsm" SVSM present */
>  
>  /* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 4d095affdb4d..e197610b4eed 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -301,6 +301,17 @@ static int get_rmpentry(u64 pfn, struct rmpread *entry)
>  {
>  	struct rmpentry *e;
>  
> +	if (cpu_feature_enabled(X86_FEATURE_RMPREAD)) {
> +		int ret;
> +
> +		asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfd"
> +			     : "=a" (ret)
> +			     : "a" (pfn << PAGE_SHIFT), "c" (entry)
> +			     : "memory", "cc");
> +
> +		return ret;
> +	}
> +
>  	e = __get_rmpentry(pfn);
>  	if (IS_ERR(e))
>  		return PTR_ERR(e);

Reviewed-by: Ashish Kalra <ashish.kalra@amd.com>

Thanks,
Ashish

Re: [PATCH v4 3/8] x86/sev: Require the RMPREAD instruction after Zen4

[Kalra, Ashish]

On 10/23/2024 1:41 PM, Tom Lendacky wrote:
> Limit usage of the non-architectural RMP format to Zen3/Zen4 processors.
> The RMPREAD instruction, with architectural defined output, is available
> and should be used for RMP access beyond Zen4.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/kernel/cpu/amd.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index fab5caec0b72..547bcdf50f1b 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -355,10 +355,15 @@ static void bsp_determine_snp(struct cpuinfo_x86 *c)
>  		/*
>  		 * RMP table entry format is not architectural and is defined by the
>  		 * per-processor PPR. Restrict SNP support on the known CPU models
> -		 * for which the RMP table entry format is currently defined for.
> +		 * for which the RMP table entry format is currently defined or for
> +		 * processors which support the architecturally defined RMPREAD
> +		 * instruction.
>  		 */
>  		if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
> -		    c->x86 >= 0x19 && snp_probe_rmptable_info()) {
> +		    (cpu_feature_enabled(X86_FEATURE_ZEN3) ||
> +		     cpu_feature_enabled(X86_FEATURE_ZEN4) ||
> +		     cpu_feature_enabled(X86_FEATURE_RMPREAD)) &&
> +		    snp_probe_rmptable_info()) {
>  			cc_platform_set(CC_ATTR_HOST_SEV_SNP);
>  		} else {
>  			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);

Reviewed-by: Ashish Kalra <ashish.kalra@amd.com>

Thanks,
Ashish

Re: [PATCH v4 5/8] x86/sev: Map only the RMP table entries instead of the full RMP range

[Kalra, Ashish]

On 10/23/2024 1:41 PM, Tom Lendacky wrote:
> In preparation for support of a segmented RMP table, map only the RMP
> table entries. The RMP bookkeeping area is only ever accessed when
> first enabling SNP and does not need to remain mapped. To accomplish
> this, split the initialization of the RMP bookkeeping area and the
> initialization of the RMP entry area. The RMP bookkeeping area will be
> mapped only while it is being initialized.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/virt/svm/sev.c | 36 +++++++++++++++++++++++++++++++-----
>  1 file changed, 31 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index d0fca9bb2e12..dd256e76e443 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -168,6 +168,23 @@ void __init snp_fixup_e820_tables(void)
>  	__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
>  }
>  
> +static bool __init init_rmptable_bookkeeping(void)
> +{
> +	void *bk;
> +
> +	bk = memremap(probed_rmp_base, RMPTABLE_CPU_BOOKKEEPING_SZ, MEMREMAP_WB);
> +	if (!bk) {
> +		pr_err("Failed to map RMP bookkeeping area\n");
> +		return false;
> +	}
> +
> +	memset(bk, 0, RMPTABLE_CPU_BOOKKEEPING_SZ);
> +
> +	memunmap(bk);
> +
> +	return true;
> +}
> +
>  /*
>   * Do the necessary preparations which are verified by the firmware as
>   * described in the SNP_INIT_EX firmware command description in the SNP
> @@ -205,12 +222,17 @@ static int __init snp_rmptable_init(void)
>  		goto nosnp;
>  	}
>  
> -	rmptable_start = memremap(probed_rmp_base, probed_rmp_size, MEMREMAP_WB);
> +	/* Map only the RMP entries */
> +	rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ,
> +				  probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ,
> +				  MEMREMAP_WB);
>  	if (!rmptable_start) {
>  		pr_err("Failed to map RMP table\n");
>  		goto nosnp;
>  	}
>  
> +	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> +
>  	/*
>  	 * Check if SEV-SNP is already enabled, this can happen in case of
>  	 * kexec boot.
> @@ -219,7 +241,14 @@ static int __init snp_rmptable_init(void)
>  	if (val & MSR_AMD64_SYSCFG_SNP_EN)
>  		goto skip_enable;
>  
> -	memset(rmptable_start, 0, probed_rmp_size);
> +	/* Zero out the RMP bookkeeping area */
> +	if (!init_rmptable_bookkeeping()) {
> +		memunmap(rmptable_start);
> +		goto nosnp;
> +	}
> +
> +	/* Zero out the RMP entries */
> +	memset(rmptable_start, 0, rmptable_size);
>  
>  	/* Flush the caches to ensure that data is written before SNP is enabled. */
>  	wbinvd_on_all_cpus();
> @@ -230,9 +259,6 @@ static int __init snp_rmptable_init(void)
>  	on_each_cpu(snp_enable, NULL, 1);
>  
>  skip_enable:
> -	rmptable_start += RMPTABLE_CPU_BOOKKEEPING_SZ;
> -	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> -
>  	rmptable = (struct rmpentry *)rmptable_start;
>  	rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry) - 1;
>  

Reviewed-by: Ashish Kalra <ashish.kalra@amd.com>

Thanks,
Ashish

Re: [PATCH v4 6/8] x86/sev: Treat the contiguous RMP table as a single RMP segment

[Kalra, Ashish]

On 10/23/2024 1:42 PM, Tom Lendacky wrote:
> In preparation for support of a segmented RMP table, treat the contiguous
> RMP table as a segmented RMP table with a single segment covering all
> of memory. By treating a contiguous RMP table as a single segment, much
> of the code that initializes and accesses the RMP can be re-used.
> 
> Segmented RMP tables can have up to 512 segment entries. Each segment
> will have metadata associated with it to identify the segment location,
> the segment size, etc. The segment data and the physical address are used
> to determine the index of the segment within the table and then the RMP
> entry within the segment. For an actual segmented RMP table environment,
> much of the segment information will come from a configuration MSR. For
> the contiguous RMP, though, much of the information will be statically
> defined.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/virt/svm/sev.c | 193 ++++++++++++++++++++++++++++++++++++----
>  1 file changed, 174 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index dd256e76e443..043b2582e10e 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -18,6 +18,7 @@
>  #include <linux/cpumask.h>
>  #include <linux/iommu.h>
>  #include <linux/amd-iommu.h>
> +#include <linux/nospec.h>
>  
>  #include <asm/sev.h>
>  #include <asm/processor.h>
> @@ -74,12 +75,42 @@ struct rmpentry {
>   */
>  #define RMPTABLE_CPU_BOOKKEEPING_SZ	0x4000
>  
> +/*
> + * For a non-segmented RMP table, use the maximum physical addressing as the
> + * segment size in order to always arrive at index 0 in the table.
> + */
> +#define RMPTABLE_NON_SEGMENTED_SHIFT	52
> +
> +struct rmp_segment_desc {
> +	struct rmpentry *rmp_entry;
> +	u64 max_index;
> +	u64 size;
> +};
> +
> +/*
> + * Segmented RMP Table support.
> + *   - The segment size is used for two purposes:
> + *     - Identify the amount of memory covered by an RMP segment
> + *     - Quickly locate an RMP segment table entry for a physical address
> + *
> + *   - The RMP segment table contains pointers to an RMP table that covers
> + *     a specific portion of memory. There can be up to 512 8-byte entries,
> + *     one pages worth.
> + */
> +static struct rmp_segment_desc **rmp_segment_table __ro_after_init;
> +static unsigned int rst_max_index __ro_after_init = 512;
> +
> +static u64 rmp_segment_size_max;
> +static unsigned int rmp_segment_coverage_shift;
> +static u64 rmp_segment_coverage_size;
> +static u64 rmp_segment_coverage_mask;
> +#define RST_ENTRY_INDEX(x)	((x) >> rmp_segment_coverage_shift)
> +#define RMP_ENTRY_INDEX(x)	((u64)(PHYS_PFN((x) & rmp_segment_coverage_mask)))
> +
>  /* Mask to apply to a PFN to get the first PFN of a 2MB page */
>  #define PFN_PMD_MASK	GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)
>  
>  static u64 probed_rmp_base, probed_rmp_size;
> -static struct rmpentry *rmptable __ro_after_init;
> -static u64 rmptable_max_pfn __ro_after_init;
>  
>  static LIST_HEAD(snp_leaked_pages_list);
>  static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
> @@ -185,6 +216,92 @@ static bool __init init_rmptable_bookkeeping(void)
>  	return true;
>  }
>  
> +static bool __init alloc_rmp_segment_desc(u64 segment_pa, u64 segment_size, u64 pa)
> +{
> +	struct rmp_segment_desc *desc;
> +	void *rmp_segment;
> +	u64 rst_index;
> +
> +	/* Validate the RMP segment size */
> +	if (segment_size > rmp_segment_size_max) {
> +		pr_err("Invalid RMP size (%#llx) for configured segment size (%#llx)\n",
> +		       segment_size, rmp_segment_size_max);
> +		return false;
> +	}
> +
> +	/* Validate the RMP segment table index */
> +	rst_index = RST_ENTRY_INDEX(pa);
> +	if (rst_index >= rst_max_index) {
> +		pr_err("Invalid RMP segment base address (%#llx) for configured segment size (%#llx)\n",
> +		       pa, rmp_segment_coverage_size);
> +		return false;
> +	}
> +	rst_index = array_index_nospec(rst_index, rst_max_index);
> +
> +	if (rmp_segment_table[rst_index]) {
> +		pr_err("RMP segment descriptor already exists at index %llu\n", rst_index);
> +		return false;
> +	}
> +
> +	/* Map the RMP entries */
> +	rmp_segment = memremap(segment_pa, segment_size, MEMREMAP_WB);
> +	if (!rmp_segment) {
> +		pr_err("Failed to map RMP segment addr 0x%llx size 0x%llx\n",
> +		       segment_pa, segment_size);
> +		return false;
> +	}
> +
> +	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
> +	if (!desc) {
> +		memunmap(rmp_segment);
> +		return false;
> +	}
> +
> +	desc->rmp_entry = rmp_segment;
> +	desc->max_index = segment_size / sizeof(*desc->rmp_entry);
> +	desc->size = segment_size;
> +
> +	/* Add the segment descriptor to the table */
> +	rmp_segment_table[rst_index] = desc;
> +
> +	return true;
> +}
> +
> +static void __init free_rmp_segment_table(void)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < rst_max_index; i++) {
> +		struct rmp_segment_desc *desc;
> +
> +		desc = rmp_segment_table[i];
> +		if (!desc)
> +			continue;
> +
> +		memunmap(desc->rmp_entry);
> +
> +		kfree(desc);
> +	}
> +
> +	free_page((unsigned long)rmp_segment_table);
> +
> +	rmp_segment_table = NULL;
> +}
> +
> +static bool __init alloc_rmp_segment_table(void)
> +{
> +	struct page *page;
> +
> +	/* Allocate the table used to index into the RMP segments */
> +	page = alloc_page(__GFP_ZERO);
> +	if (!page)
> +		return false;
> +
> +	rmp_segment_table = page_address(page);
> +
> +	return true;
> +}
> +
>  /*
>   * Do the necessary preparations which are verified by the firmware as
>   * described in the SNP_INIT_EX firmware command description in the SNP
> @@ -192,8 +309,8 @@ static bool __init init_rmptable_bookkeeping(void)
>   */
>  static int __init snp_rmptable_init(void)
>  {
> -	u64 max_rmp_pfn, calc_rmp_sz, rmptable_size, rmp_end, val;
> -	void *rmptable_start;
> +	u64 max_rmp_pfn, calc_rmp_sz, rmptable_segment, rmptable_size, rmp_end, val;
> +	unsigned int i;
>  
>  	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>  		return 0;
> @@ -222,17 +339,18 @@ static int __init snp_rmptable_init(void)
>  		goto nosnp;
>  	}
>  
> +	if (!alloc_rmp_segment_table())
> +		goto nosnp;
> +
>  	/* Map only the RMP entries */
> -	rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ,
> -				  probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ,
> -				  MEMREMAP_WB);
> -	if (!rmptable_start) {
> -		pr_err("Failed to map RMP table\n");
> +	rmptable_segment = probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ;
> +	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> +
> +	if (!alloc_rmp_segment_desc(rmptable_segment, rmptable_size, 0)) {
> +		free_rmp_segment_table();
>  		goto nosnp;
>  	}
>  
> -	rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> -
>  	/*
>  	 * Check if SEV-SNP is already enabled, this can happen in case of
>  	 * kexec boot.
> @@ -243,12 +361,20 @@ static int __init snp_rmptable_init(void)
>  
>  	/* Zero out the RMP bookkeeping area */
>  	if (!init_rmptable_bookkeeping()) {
> -		memunmap(rmptable_start);
> +		free_rmp_segment_table();
>  		goto nosnp;
>  	}
>  
>  	/* Zero out the RMP entries */
> -	memset(rmptable_start, 0, rmptable_size);
> +	for (i = 0; i < rst_max_index; i++) {
> +		struct rmp_segment_desc *desc;
> +
> +		desc = rmp_segment_table[i];
> +		if (!desc)
> +			continue;
> +
> +		memset(desc->rmp_entry, 0, desc->size);
> +	}
>  
>  	/* Flush the caches to ensure that data is written before SNP is enabled. */
>  	wbinvd_on_all_cpus();
> @@ -259,9 +385,6 @@ static int __init snp_rmptable_init(void)
>  	on_each_cpu(snp_enable, NULL, 1);
>  
>  skip_enable:
> -	rmptable = (struct rmpentry *)rmptable_start;
> -	rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry) - 1;
> -
>  	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);
>  
>  	/*
> @@ -282,6 +405,17 @@ static int __init snp_rmptable_init(void)
>   */
>  device_initcall(snp_rmptable_init);
>  
> +static void set_rmp_segment_info(unsigned int segment_shift)
> +{
> +	rmp_segment_coverage_shift = segment_shift;
> +	rmp_segment_coverage_size  = 1ULL << rmp_segment_coverage_shift;
> +	rmp_segment_coverage_mask  = rmp_segment_coverage_size - 1;
> +
> +	/* Calculate the maximum size an RMP can be (16 bytes/page mapped) */
> +	rmp_segment_size_max = PHYS_PFN(rmp_segment_coverage_size);
> +	rmp_segment_size_max <<= 4;
> +}
> +
>  #define RMP_ADDR_MASK GENMASK_ULL(51, 13)
>  
>  bool snp_probe_rmptable_info(void)
> @@ -303,6 +437,11 @@ bool snp_probe_rmptable_info(void)
>  
>  	rmp_sz = rmp_end - rmp_base + 1;
>  
> +	/* Treat the contiguous RMP table as a single segment */
> +	rst_max_index = 1;
> +
> +	set_rmp_segment_info(RMPTABLE_NON_SEGMENTED_SHIFT);
> +
>  	probed_rmp_base = rmp_base;
>  	probed_rmp_size = rmp_sz;
>  
> @@ -314,13 +453,29 @@ bool snp_probe_rmptable_info(void)
>  
>  static struct rmpentry *__get_rmpentry(u64 pfn)
>  {
> -	if (!rmptable)
> +	struct rmp_segment_desc *desc;
> +	u64 paddr, rst_index, segment_index;
> +
> +	if (!rmp_segment_table)
>  		return ERR_PTR(-ENODEV);
>  
> -	if (unlikely(pfn > rmptable_max_pfn))
> +	paddr = pfn << PAGE_SHIFT;
> +
> +	rst_index = RST_ENTRY_INDEX(paddr);
> +	if (unlikely(rst_index >= rst_max_index))
> +		return ERR_PTR(-EFAULT);
> +	rst_index = array_index_nospec(rst_index, rst_max_index);
> +
> +	desc = rmp_segment_table[rst_index];
> +	if (unlikely(!desc))
>  		return ERR_PTR(-EFAULT);
>  
> -	return rmptable + pfn;
> +	segment_index = RMP_ENTRY_INDEX(paddr);
> +	if (unlikely(segment_index >= desc->max_index))
> +		return ERR_PTR(-EFAULT);
> +	segment_index = array_index_nospec(segment_index, desc->max_index);
> +
> +	return desc->rmp_entry + segment_index;
>  }
>  

Ah ok, __get_rmpentry() is finalized here in this patch and rmptable & rmptable_max_pfn 
are removed as part of this patch, so probably my comments on patch #1 are not relevant. 

This is somewhat confusing, maybe some comments can be added in patch #1 to explain that
__get_rmpentry() will be finalized in this patch ?

My confusion results from the following : 

Patch #1: 
__get_rmpentry() 
--- refers to rmptable.

Patch #5:
rmptable initialized here.

Patch #6:
rmptable not required and removed in this patch.
do final cleanup for __get_rmpentry(). 

Thanks,
Ashish

>  static int get_rmpentry(u64 pfn, struct rmpread *entry)

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Borislav Petkov]

On Wed, Oct 23, 2024 at 01:41:55PM -0500, Tom Lendacky wrote:
> +/*
> + * The RMP entry format as returned by the RMPREAD instruction.
> + */
> +struct rmpread {

Hmm, I'm not sure this is better. "rmread" is an instruction but then you have
a struct called this way too. Strange. :-\

I think you almost had it already with a little more explanations:

https://lore.kernel.org/r/20241018111043.GAZxJCM8DK-wEjDJZR@fat_crate.local

The convention being that the _raw entry is what's in the actual table and
rmpentry is what RMPREAD returns. I think this is waaay more natural.

Hmmm.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Tom Lendacky]

On 10/25/24 04:00, Kalra, Ashish wrote:
> , 
> On 10/23/2024 1:41 PM, Tom Lendacky wrote:
>> The RMPREAD instruction returns an architecture defined format of an
>> RMP entry. This is the preferred method for examining RMP entries.
>>
>> In preparation for using the RMPREAD instruction, convert the existing
>> code that directly accesses the RMP to map the raw RMP information into
>> the architecture defined format.
>>
>> RMPREAD output returns a status bit for the 2MB region status. If the
>> input page address is 2MB aligned and any other pages within the 2MB
>> region are assigned, then 2MB region status will be set to 1. Otherwise,
>> the 2MB region status will be set to 0. For systems that do not support
>> RMPREAD, calculating this value would require looping over all of the RMP
>> table entries within that range until one is found with the assigned bit
>> set. Since this bit is not defined in the current format, and so not used
>> today, do not incur the overhead associated with calculating it.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>>  arch/x86/virt/svm/sev.c | 121 +++++++++++++++++++++++++++++-----------
>>  1 file changed, 87 insertions(+), 34 deletions(-)
>>
>> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
>> index 0ce17766c0e5..4d095affdb4d 100644
>> --- a/arch/x86/virt/svm/sev.c
>> +++ b/arch/x86/virt/svm/sev.c

>>  
>> -	entry = get_rmpentry(pfn);
>> -	if (IS_ERR(entry))
>> -		return entry;
>> +	if (unlikely(pfn > rmptable_max_pfn))
> 
> rmptable_max_pfn is initialized in patch#5, shouldn't this patch be moved after patch #5 ?
> 
>> +		return ERR_PTR(-EFAULT);
>> +
>> +	return rmptable + pfn;
> 
> Again, rmptable is initialized/setup in patch#5, similarly shouldn't this patch be moved
> after patch #5 ?

rmptable_max_pfn is initialized in snp_rmptable_init(), as is rmptable.

Thanks,
Tom

> 
> Thanks,
> Ashish
> 

Re: [PATCH v4 6/8] x86/sev: Treat the contiguous RMP table as a single RMP segment

[Tom Lendacky]

On 10/25/24 06:51, Kalra, Ashish wrote:
> On 10/23/2024 1:42 PM, Tom Lendacky wrote:
>> In preparation for support of a segmented RMP table, treat the contiguous
>> RMP table as a segmented RMP table with a single segment covering all
>> of memory. By treating a contiguous RMP table as a single segment, much
>> of the code that initializes and accesses the RMP can be re-used.
>>
>> Segmented RMP tables can have up to 512 segment entries. Each segment
>> will have metadata associated with it to identify the segment location,
>> the segment size, etc. The segment data and the physical address are used
>> to determine the index of the segment within the table and then the RMP
>> entry within the segment. For an actual segmented RMP table environment,
>> much of the segment information will come from a configuration MSR. For
>> the contiguous RMP, though, much of the information will be statically
>> defined.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>>  arch/x86/virt/svm/sev.c | 193 ++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 174 insertions(+), 19 deletions(-)
>>
>> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
>> index dd256e76e443..043b2582e10e 100644
>> --- a/arch/x86/virt/svm/sev.c
>> +++ b/arch/x86/virt/svm/sev.c

>> -	return rmptable + pfn;
>> +	segment_index = RMP_ENTRY_INDEX(paddr);
>> +	if (unlikely(segment_index >= desc->max_index))
>> +		return ERR_PTR(-EFAULT);
>> +	segment_index = array_index_nospec(segment_index, desc->max_index);
>> +
>> +	return desc->rmp_entry + segment_index;
>>  }
>>  
> 
> Ah ok, __get_rmpentry() is finalized here in this patch and rmptable & rmptable_max_pfn 
> are removed as part of this patch, so probably my comments on patch #1 are not relevant. 
> 
> This is somewhat confusing, maybe some comments can be added in patch #1 to explain that
> __get_rmpentry() will be finalized in this patch ?
> 
> My confusion results from the following : 
> 
> Patch #1: 
> __get_rmpentry() 
> --- refers to rmptable.
> 
> Patch #5:
> rmptable initialized here.
> 
> Patch #6:
> rmptable not required and removed in this patch.
> do final cleanup for __get_rmpentry(). 

Patch #1 was just a restructuring, rmptable_max_pfn and rmptable are both
initialized in snp_rmptable_init() as they previously were. So no real
explanation needed.

Thanks,
Tom

> 
> Thanks,
> Ashish
> 
>>  static int get_rmpentry(u64 pfn, struct rmpread *entry)

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Tom Lendacky]

On 10/25/24 07:09, Borislav Petkov wrote:
> On Wed, Oct 23, 2024 at 01:41:55PM -0500, Tom Lendacky wrote:
>> +/*
>> + * The RMP entry format as returned by the RMPREAD instruction.
>> + */
>> +struct rmpread {
> 
> Hmm, I'm not sure this is better. "rmread" is an instruction but then you have
> a struct called this way too. Strange. :-\
> 
> I think you almost had it already with a little more explanations:
> 
> https://lore.kernel.org/r/20241018111043.GAZxJCM8DK-wEjDJZR@fat_crate.local
> 
> The convention being that the _raw entry is what's in the actual table and
> rmpentry is what RMPREAD returns. I think this is waaay more natural.
> 
> Hmmm.

Just wanted to show you what it looks like. There still is a lot of change
because of the new argument and using a structure now instead of the
direct entry.

I can change back and maybe add some more detail above the struct names if
that suffices.

Thanks,
Tom

> 

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Borislav Petkov]

On Fri, Oct 25, 2024 at 08:47:06AM -0500, Tom Lendacky wrote:
> Just wanted to show you what it looks like. There still is a lot of change
> because of the new argument and using a structure now instead of the
> direct entry.

Ah ok.

> I can change back and maybe add some more detail above the struct names if
> that suffices.

Yeah, I think "struct rmpread" is simply a strange thing to have when there is
an instruction of that name. I think the naming of the structs should aim at
being descriptive as to what they are. Hypothetical example:

struct rmpentry_as_found_in_the_rmptable ...

struct rmpentry_as_returned_by_rmpread

Now make the above shorter by keeping the information. :-)

IOW, on the one hand, "rmpentry_raw" or "rmpentry_direct" or
"rmpentry_<something>", and, OTOH, just "struct rmpentry" kinda makes sense
and it is short enough.

At least how I see it rn...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Tom Lendacky]

On 10/25/24 08:47, Tom Lendacky wrote:
> On 10/25/24 07:09, Borislav Petkov wrote:
>> On Wed, Oct 23, 2024 at 01:41:55PM -0500, Tom Lendacky wrote:
>>> +/*
>>> + * The RMP entry format as returned by the RMPREAD instruction.
>>> + */
>>> +struct rmpread {
>>
>> Hmm, I'm not sure this is better. "rmread" is an instruction but then you have
>> a struct called this way too. Strange. :-\
>>
>> I think you almost had it already with a little more explanations:
>>
>> https://lore.kernel.org/r/20241018111043.GAZxJCM8DK-wEjDJZR@fat_crate.local

And why am I not getting the replies you made to the v2 series but getting
replies to the v3 and v4 series...  very frustrating... can't find them in
quarantine or anywhere, dang email system.

Thanks,
Tom

>>
>> The convention being that the _raw entry is what's in the actual table and
>> rmpentry is what RMPREAD returns. I think this is waaay more natural.
>>
>> Hmmm.
> 
> Just wanted to show you what it looks like. There still is a lot of change
> because of the new argument and using a structure now instead of the
> direct entry.
> 
> I can change back and maybe add some more detail above the struct names if
> that suffices.
> 
> Thanks,
> Tom
> 
>>

Re: [PATCH v4 1/8] x86/sev: Prepare for using the RMPREAD instruction to access the RMP

[Borislav Petkov]

On Fri, Oct 25, 2024 at 08:56:09AM -0500, Tom Lendacky wrote:
> And why am I not getting the replies you made to the v2 series but getting
> replies to the v3 and v4 series...  very frustrating... can't find them in
> quarantine or anywhere, dang email system.

You can always switch to an email system which works for kernel development
and use the corporate thing for something else.

Like I do.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette