[PATCH 10/15] swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction

Christoph Hellwig
2022-03-14T07:32:41Z

Power SVM wants to allocate a swiotlb buffer that is not restricted to
low memory for the trusted hypervisor scheme. Consolidate the support
for this into the swiotlb_init interface by adding a new flag.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/powerpc/include/asm/svm.h | 4 ----
arch/powerpc/include/asm/swiotlb.h | 1 +
arch/powerpc/kernel/dma-swiotlb.c | 1 +
arch/powerpc/mm/mem.c | 5 +----
arch/powerpc/platforms/pseries/svm.c | 26 +-------------------------
include/linux/swiotlb.h | 1 +
kernel/dma/swiotlb.c | 11 +++++++++--
7 files changed, 14 insertions(+), 35 deletions(-)

diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 7546402d796af..85580b30aba48 100644
--- a/arch/powerpc/include/asm/svm.h
+++ b/arch/powerpc/include/asm/svm.h
@@ -15,8 +15,6 @@ static inline bool is_secure_guest(void)
return mfmsr() & MSR_S;
}

-void __init svm_swiotlb_init(void);
-
void dtl_cache_ctor(void *addr);
#define get_dtl_cache_ctor() (is_secure_guest() ? dtl_cache_ctor : NULL)

@@ -27,8 +25,6 @@ static inline bool is_secure_guest(void)
return false;
}

-static inline void svm_swiotlb_init(void) {}
-
#define get_dtl_cache_ctor() NULL

#endif /* CONFIG_PPC_SVM */
diff --git a/arch/powerpc/include/asm/swiotlb.h b/arch/powerpc/include/asm/swiotlb.h
index 3c1a1cd161286..4203b5e0a88ed 100644
--- a/arch/powerpc/include/asm/swiotlb.h
+++ b/arch/powerpc/include/asm/swiotlb.h
@@ -9,6 +9,7 @@
#include <linux/swiotlb.h>

extern unsigned int ppc_swiotlb_enable;
+extern unsigned int ppc_swiotlb_flags;

#ifdef CONFIG_SWIOTLB
void swiotlb_detect_4g(void);
diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c
index fc7816126a401..ba256c37bcc0f 100644
--- a/arch/powerpc/kernel/dma-swiotlb.c
+++ b/arch/powerpc/kernel/dma-swiotlb.c
@@ -10,6 +10,7 @@
#include <asm/swiotlb.h>

unsigned int ppc_swiotlb_enable;
+unsigned int ppc_swiotlb_flags;

void __init swiotlb_detect_4g(void)
{
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index e1519e2edc656..a4d65418c30a9 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -249,10 +249,7 @@ void __init mem_init(void)
* back to to-down.
*/
memblock_set_bottom_up(true);
- if (is_secure_guest())
- svm_swiotlb_init();
- else
- swiotlb_init(ppc_swiotlb_enable, 0);
+ swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags);
#endif

high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
index c5228f4969eb2..3b4045d508ec8 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -28,7 +28,7 @@ static int __init init_svm(void)
* need to use the SWIOTLB buffer for DMA even if dma_capable() says
* otherwise.
*/
- swiotlb_force = SWIOTLB_FORCE;
+ ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;

/* Share the SWIOTLB buffer with the host. */
swiotlb_update_mem_attributes();
@@ -37,30 +37,6 @@ static int __init init_svm(void)
}
machine_early_initcall(pseries, init_svm);

-/*
- * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it
- * can allocate the buffer anywhere in memory. Since the hypervisor doesn't have
- * any addressing limitation, we don't need to allocate it in low addresses.
- */
-void __init svm_swiotlb_init(void)
-{
- unsigned char *vstart;
- unsigned long bytes, io_tlb_nslabs;
-
- io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT);
- io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
-
- bytes = io_tlb_nslabs << IO_TLB_SHIFT;
-
- vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
- if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
- return;
-
-
- memblock_free(vstart, PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
- panic("SVM: Cannot allocate SWIOTLB buffer");
-}
-
int set_memory_encrypted(unsigned long addr, int numpages)
{
if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT))
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index ae0407173e845..eabdd89987027 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -15,6 +15,7 @@ struct scatterlist;

#define SWIOTLB_VERBOSE (1 << 0) /* verbose initialization */
#define SWIOTLB_FORCE (1 << 1) /* force bounce buffering */
+#define SWIOTLB_ANY (1 << 2) /* allow any memory for the buffer */

/*
* Maximum allowable number of contiguous slabs to map,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 5ac6e128d4279..2ad12562c94fe 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -266,8 +266,15 @@ void __init swiotlb_init(bool addressing_limit, unsigned int flags)
if (swiotlb_force_disable)
return;

- /* Get IO TLB memory from the low pages */
- tlb = memblock_alloc_low(bytes, PAGE_SIZE);
+ /*
+ * By default allocate the bounce buffer memory from low memory, but
+ * allow to pick a location everywhere for hypervisors with guest
+ * memory encryption.
+ */
+ if (flags & SWIOTLB_ANY)
+ tlb = memblock_alloc(bytes, PAGE_SIZE);
+ else
+ tlb = memblock_alloc_low(bytes, PAGE_SIZE);
if (!tlb)
goto fail;
if (swiotlb_init_with_tbl(tlb, default_nslabs, flags))
--
2.30.2