Re: [PATCH v2 1/2] x86/sev: Move sev_setup_arch() to mem_encrypt.c

From: Tom Lendacky
Date: Mon Aug 14 2023 - 16:22:22 EST

On 6/9/23 12:12, Alexander Shishkin wrote:
Since commit 4d96f9109109b ("x86/sev: Replace occurrences of
sev_active() with cc_platform_has()"), the SWIOTLB bounce buffer size
adjustment and restricted virtio memory setting also inadvertently apply
to TDX: the code is using cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) as
a gatekeeping condition, which is also true for TDX, and this is also what
we want.

To reflect this, move the corresponding code to generic mem_encrypt.c.
No functional changes intended.

Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/mem_encrypt.h | 11 ++++++++--
arch/x86/kernel/setup.c | 2 +-
arch/x86/mm/mem_encrypt.c | 34 +++++++++++++++++++++++++++++
arch/x86/mm/mem_encrypt_amd.c | 35 ------------------------------
4 files changed, 44 insertions(+), 38 deletions(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index b7126701574c..4283063c1e1c 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -37,7 +37,6 @@ void __init sme_map_bootdata(char *real_mode_data);
void __init sme_unmap_bootdata(char *real_mode_data);
void __init sme_early_init(void);
-void __init sev_setup_arch(void);
void __init sme_encrypt_kernel(struct boot_params *bp);
void __init sme_enable(struct boot_params *bp);
@@ -67,7 +66,6 @@ static inline void __init sme_map_bootdata(char *real_mode_data) { }
static inline void __init sme_unmap_bootdata(char *real_mode_data) { }
static inline void __init sme_early_init(void) { }
-static inline void __init sev_setup_arch(void) { }
static inline void __init sme_encrypt_kernel(struct boot_params *bp) { }
static inline void __init sme_enable(struct boot_params *bp) { }
@@ -92,6 +90,15 @@ void __init mem_encrypt_init(void);
void add_encrypt_protection_map(void);
+#ifdef CONFIG_X86_MEM_ENCRYPT
+
+void __init mem_encrypt_setup_arch(void);
+
+#else /* !CONFIG_X86_MEM_ENCRYPT */
+
+static inline void __init mem_encrypt_setup_arch(void) { }
+
+#endif /* CONFIG_X86_MEM_ENCRYPT */

Commit 0a9567ac5e6a ("x86/mem_encrypt: Unbreak the AMD_MEM_ENCRYPT=n build") added a #ifdef for CONFIG_X86_MEM_ENCRYPT near the top of the file, it would be better to rebase and put these up with the mem_encrypt_init() definitions.

Otherwise, no objections.

Thanks,
Tom

/*
* The __sme_pa() and __sme_pa_nodebug() macros are meant for use when
* writing to or comparing values from the cr3 register. Having the
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 16babff771bd..e2aa1d5b37a9 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1121,7 +1121,7 @@ void __init setup_arch(char **cmdline_p)
* Needs to run after memblock setup because it needs the physical
* memory size.
*/
- sev_setup_arch();
+ mem_encrypt_setup_arch();
efi_fake_memmap();
efi_find_mirror();
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 9f27e14e185f..c290c55b632b 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -12,6 +12,7 @@
#include <linux/swiotlb.h>
#include <linux/cc_platform.h>
#include <linux/mem_encrypt.h>
+#include <linux/virtio_anchor.h>
/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
bool force_dma_unencrypted(struct device *dev)
@@ -86,3 +87,36 @@ void __init mem_encrypt_init(void)
print_mem_encrypt_feature_info();
}
+
+void __init mem_encrypt_setup_arch(void)
+{
+ phys_addr_t total_mem = memblock_phys_mem_size();
+ unsigned long size;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+ return;
+
+ /*
+ * For SEV and TDX, all DMA has to occur via shared/unencrypted pages.
+ * Kernel uses SWIOTLB to make this happen without changing device
+ * drivers. However, depending on the workload being run, the
+ * default 64MB of SWIOTLB may not be enough and SWIOTLB may
+ * run out of buffers for DMA, resulting in I/O errors and/or
+ * performance degradation especially with high I/O workloads.
+ *
+ * Adjust the default size of SWIOTLB using a percentage of guest
+ * memory for SWIOTLB buffers. Also, as the SWIOTLB bounce buffer
+ * memory is allocated from low memory, ensure that the adjusted size
+ * is within the limits of low available memory.
+ *
+ * The percentage of guest memory used here for SWIOTLB buffers
+ * is more of an approximation of the static adjustment which
+ * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
+ */
+ size = total_mem * 6 / 100;
+ size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
+ swiotlb_adjust_size(size);
+
+ /* Set restricted memory access for virtio. */
+ virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
+}
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index e0b51c09109f..b1edeb8642b8 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -20,7 +20,6 @@
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
#include <linux/virtio_config.h>
-#include <linux/virtio_anchor.h>
#include <linux/cc_platform.h>
#include <asm/tlbflush.h>
@@ -215,40 +214,6 @@ void __init sme_map_bootdata(char *real_mode_data)
__sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, true);
}
-void __init sev_setup_arch(void)
-{
- phys_addr_t total_mem = memblock_phys_mem_size();
- unsigned long size;
-
- if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
- return;
-
- /*
- * For SEV, all DMA has to occur via shared/unencrypted pages.
- * SEV uses SWIOTLB to make this happen without changing device
- * drivers. However, depending on the workload being run, the
- * default 64MB of SWIOTLB may not be enough and SWIOTLB may
- * run out of buffers for DMA, resulting in I/O errors and/or
- * performance degradation especially with high I/O workloads.
- *
- * Adjust the default size of SWIOTLB for SEV guests using
- * a percentage of guest memory for SWIOTLB buffers.
- * Also, as the SWIOTLB bounce buffer memory is allocated
- * from low memory, ensure that the adjusted size is within
- * the limits of low available memory.
- *
- * The percentage of guest memory used here for SWIOTLB buffers
- * is more of an approximation of the static adjustment which
- * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
- */
- size = total_mem * 6 / 100;
- size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
- swiotlb_adjust_size(size);
-
- /* Set restricted memory access for virtio. */
- virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
-}
-
static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
{
unsigned long pfn = 0;