[GIT PULL] x86 fixes

Ingo Molnar
2023-10-08T09:42:02Z

Linus,

Please pull the latest x86/urgent git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-2023-10-08

# HEAD: 62d5e970d022ef4bde18948dd67247c3194384c1 x86/sev: Change npages to unsigned long in snp_accept_memory()

Misc fixes:

- Fix SEV-SNP guest crashes that may happen on NMIs

- Fix a potential SEV platform memory setup overflow

Thanks,

Ingo

------------------>
Tom Lendacky (2):
x86/sev: Use the GHCB protocol when available for SNP CPUID requests
x86/sev: Change npages to unsigned long in snp_accept_memory()

arch/x86/kernel/sev-shared.c | 69 +++++++++++++++++++++++++++++++++++---------
arch/x86/kernel/sev.c | 3 +-
2 files changed, 56 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 2eabccde94fb..dcf325b7b022 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -256,7 +256,7 @@ static int __sev_cpuid_hv(u32 fn, int reg_idx, u32 *reg)
return 0;
}

-static int sev_cpuid_hv(struct cpuid_leaf *leaf)
+static int __sev_cpuid_hv_msr(struct cpuid_leaf *leaf)
{
int ret;

@@ -279,6 +279,45 @@ static int sev_cpuid_hv(struct cpuid_leaf *leaf)
return ret;
}

+static int __sev_cpuid_hv_ghcb(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
+{
+ u32 cr4 = native_read_cr4();
+ int ret;
+
+ ghcb_set_rax(ghcb, leaf->fn);
+ ghcb_set_rcx(ghcb, leaf->subfn);
+
+ if (cr4 & X86_CR4_OSXSAVE)
+ /* Safe to read xcr0 */
+ ghcb_set_xcr0(ghcb, xgetbv(XCR_XFEATURE_ENABLED_MASK));
+ else
+ /* xgetbv will cause #UD - use reset value for xcr0 */
+ ghcb_set_xcr0(ghcb, 1);
+
+ ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
+ if (ret != ES_OK)
+ return ret;
+
+ if (!(ghcb_rax_is_valid(ghcb) &&
+ ghcb_rbx_is_valid(ghcb) &&
+ ghcb_rcx_is_valid(ghcb) &&
+ ghcb_rdx_is_valid(ghcb)))
+ return ES_VMM_ERROR;
+
+ leaf->eax = ghcb->save.rax;
+ leaf->ebx = ghcb->save.rbx;
+ leaf->ecx = ghcb->save.rcx;
+ leaf->edx = ghcb->save.rdx;
+
+ return ES_OK;
+}
+
+static int sev_cpuid_hv(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
+{
+ return ghcb ? __sev_cpuid_hv_ghcb(ghcb, ctxt, leaf)
+ : __sev_cpuid_hv_msr(leaf);
+}
+
/*
* This may be called early while still running on the initial identity
* mapping. Use RIP-relative addressing to obtain the correct address
@@ -388,19 +427,20 @@ snp_cpuid_get_validated_func(struct cpuid_leaf *leaf)
return false;
}

-static void snp_cpuid_hv(struct cpuid_leaf *leaf)
+static void snp_cpuid_hv(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
{
- if (sev_cpuid_hv(leaf))
+ if (sev_cpuid_hv(ghcb, ctxt, leaf))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID_HV);
}

-static int snp_cpuid_postprocess(struct cpuid_leaf *leaf)
+static int snp_cpuid_postprocess(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
+ struct cpuid_leaf *leaf)
{
struct cpuid_leaf leaf_hv = *leaf;

switch (leaf->fn) {
case 0x1:
- snp_cpuid_hv(&leaf_hv);
+ snp_cpuid_hv(ghcb, ctxt, &leaf_hv);

/* initial APIC ID */
leaf->ebx = (leaf_hv.ebx & GENMASK(31, 24)) | (leaf->ebx & GENMASK(23, 0));
@@ -419,7 +459,7 @@ static int snp_cpuid_postprocess(struct cpuid_leaf *leaf)
break;
case 0xB:
leaf_hv.subfn = 0;
- snp_cpuid_hv(&leaf_hv);
+ snp_cpuid_hv(ghcb, ctxt, &leaf_hv);

/* extended APIC ID */
leaf->edx = leaf_hv.edx;
@@ -467,7 +507,7 @@ static int snp_cpuid_postprocess(struct cpuid_leaf *leaf)
}
break;
case 0x8000001E:
- snp_cpuid_hv(&leaf_hv);
+ snp_cpuid_hv(ghcb, ctxt, &leaf_hv);

/* extended APIC ID */
leaf->eax = leaf_hv.eax;
@@ -488,7 +528,7 @@ static int snp_cpuid_postprocess(struct cpuid_leaf *leaf)
* Returns -EOPNOTSUPP if feature not enabled. Any other non-zero return value
* should be treated as fatal by caller.
*/
-static int snp_cpuid(struct cpuid_leaf *leaf)
+static int snp_cpuid(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();

@@ -522,7 +562,7 @@ static int snp_cpuid(struct cpuid_leaf *leaf)
return 0;
}

- return snp_cpuid_postprocess(leaf);
+ return snp_cpuid_postprocess(ghcb, ctxt, leaf);
}

/*
@@ -544,14 +584,14 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
leaf.fn = fn;
leaf.subfn = subfn;

- ret = snp_cpuid(&leaf);
+ ret = snp_cpuid(NULL, NULL, &leaf);
if (!ret)
goto cpuid_done;

if (ret != -EOPNOTSUPP)
goto fail;

- if (sev_cpuid_hv(&leaf))
+ if (__sev_cpuid_hv_msr(&leaf))
goto fail;

cpuid_done:
@@ -848,14 +888,15 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
return ret;
}

-static int vc_handle_cpuid_snp(struct pt_regs *regs)
+static int vc_handle_cpuid_snp(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
+ struct pt_regs *regs = ctxt->regs;
struct cpuid_leaf leaf;
int ret;

leaf.fn = regs->ax;
leaf.subfn = regs->cx;
- ret = snp_cpuid(&leaf);
+ ret = snp_cpuid(ghcb, ctxt, &leaf);
if (!ret) {
regs->ax = leaf.eax;
regs->bx = leaf.ebx;
@@ -874,7 +915,7 @@ static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
enum es_result ret;
int snp_cpuid_ret;

- snp_cpuid_ret = vc_handle_cpuid_snp(regs);
+ snp_cpuid_ret = vc_handle_cpuid_snp(ghcb, ctxt);
if (!snp_cpuid_ret)
return ES_OK;
if (snp_cpuid_ret != -EOPNOTSUPP)
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 2787826d9f60..d8c1e3be74c0 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -868,8 +868,7 @@ void snp_set_memory_private(unsigned long vaddr, unsigned long npages)

void snp_accept_memory(phys_addr_t start, phys_addr_t end)
{
- unsigned long vaddr;
- unsigned int npages;
+ unsigned long vaddr, npages;

if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return;