Re: [PATCH v13 09/12] mm: x86: Invoke hypercall when page encryption status is changed

From: Paolo Bonzini
Date: Tue Apr 20 2021 - 05:40:28 EST

On 15/04/21 17:57, Ashish Kalra wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx>

Invoke a hypercall when a memory region is changed from encrypted ->
decrypted and vice versa. Hypervisor needs to know the page encryption
status during the guest migration.

Boris, can you ack this patch?

Paolo

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Steve Rutherford <srutherford@xxxxxxxxxx>
Reviewed-by: Venu Busireddy <venu.busireddy@xxxxxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
arch/x86/include/asm/paravirt.h | 10 +++++
arch/x86/include/asm/paravirt_types.h | 2 +
arch/x86/kernel/paravirt.c | 1 +
arch/x86/mm/mem_encrypt.c | 57 ++++++++++++++++++++++++++-
arch/x86/mm/pat/set_memory.c | 7 ++++
5 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 4abf110e2243..efaa3e628967 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -84,6 +84,12 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
PVOP_VCALL1(mmu.exit_mmap, mm);
}
+static inline void page_encryption_changed(unsigned long vaddr, int npages,
+ bool enc)
+{
+ PVOP_VCALL3(mmu.page_encryption_changed, vaddr, npages, enc);
+}
+
#ifdef CONFIG_PARAVIRT_XXL
static inline void load_sp0(unsigned long sp0)
{
@@ -799,6 +805,10 @@ static inline void paravirt_arch_dup_mmap(struct mm_struct *oldmm,
static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
{
}
+
+static inline void page_encryption_changed(unsigned long vaddr, int npages, bool enc)
+{
+}
#endif
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_PARAVIRT_H */
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index de87087d3bde..69ef9c207b38 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -195,6 +195,8 @@ struct pv_mmu_ops {
/* Hook for intercepting the destruction of an mm_struct. */
void (*exit_mmap)(struct mm_struct *mm);
+ void (*page_encryption_changed)(unsigned long vaddr, int npages,
+ bool enc);
#ifdef CONFIG_PARAVIRT_XXL
struct paravirt_callee_save read_cr2;
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c60222ab8ab9..9f206e192f6b 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -335,6 +335,7 @@ struct paravirt_patch_template pv_ops = {
(void (*)(struct mmu_gather *, void *))tlb_remove_page,
.mmu.exit_mmap = paravirt_nop,
+ .mmu.page_encryption_changed = paravirt_nop,
#ifdef CONFIG_PARAVIRT_XXL
.mmu.read_cr2 = __PV_IS_CALLEE_SAVE(native_read_cr2),
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index ae78cef79980..fae9ccbd0da7 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -19,6 +19,7 @@
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
+#include <linux/kvm_para.h>
#include <asm/tlbflush.h>
#include <asm/fixmap.h>
@@ -29,6 +30,7 @@
#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/cmdline.h>
+#include <asm/kvm_para.h>
#include "mm_internal.h"
@@ -229,6 +231,47 @@ void __init sev_setup_arch(void)
swiotlb_adjust_size(size);
}
+static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
+ bool enc)
+{
+ unsigned long sz = npages << PAGE_SHIFT;
+ unsigned long vaddr_end, vaddr_next;
+
+ vaddr_end = vaddr + sz;
+
+ for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+ int psize, pmask, level;
+ unsigned long pfn;
+ pte_t *kpte;
+
+ kpte = lookup_address(vaddr, &level);
+ if (!kpte || pte_none(*kpte))
+ return;
+
+ switch (level) {
+ case PG_LEVEL_4K:
+ pfn = pte_pfn(*kpte);
+ break;
+ case PG_LEVEL_2M:
+ pfn = pmd_pfn(*(pmd_t *)kpte);
+ break;
+ case PG_LEVEL_1G:
+ pfn = pud_pfn(*(pud_t *)kpte);
+ break;
+ default:
+ return;
+ }
+
+ psize = page_level_size(level);
+ pmask = page_level_mask(level);
+
+ kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+ pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+ vaddr_next = (vaddr & pmask) + psize;
+ }
+}
+
static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
{
pgprot_t old_prot, new_prot;
@@ -286,12 +329,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
static int __init early_set_memory_enc_dec(unsigned long vaddr,
unsigned long size, bool enc)
{
- unsigned long vaddr_end, vaddr_next;
+ unsigned long vaddr_end, vaddr_next, start;
unsigned long psize, pmask;
int split_page_size_mask;
int level, ret;
pte_t *kpte;
+ start = vaddr;
vaddr_next = vaddr;
vaddr_end = vaddr + size;
@@ -346,6 +390,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
ret = 0;
+ set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+ enc);
out:
__flush_tlb_all();
return ret;
@@ -481,6 +527,15 @@ void __init mem_encrypt_init(void)
if (sev_active() && !sev_es_active())
static_branch_enable(&sev_enable_key);
+#ifdef CONFIG_PARAVIRT
+ /*
+ * With SEV, we need to make a hypercall when page encryption state is
+ * changed.
+ */
+ if (sev_active())
+ pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
+#endif
+
print_mem_encrypt_feature_info();
}
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 16f878c26667..3576b583ac65 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -27,6 +27,7 @@
#include <asm/proto.h>
#include <asm/memtype.h>
#include <asm/set_memory.h>
+#include <asm/paravirt.h>
#include "../mm_internal.h"
@@ -2012,6 +2013,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
*/
cpa_flush(&cpa, 0);
+ /* Notify hypervisor that a given memory range is mapped encrypted
+ * or decrypted. The hypervisor will use this information during the
+ * VM migration.
+ */
+ page_encryption_changed(addr, numpages, enc);
+
return ret;
}