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Date: Fri, 3 Apr 2020 21:30:09 +0000
From: Ashish Kalra <ashish.kalra@....com>
To: Krish Sadhukhan <krish.sadhukhan@...cle.com>
Cc: pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com,
hpa@...or.com, joro@...tes.org, bp@...e.de,
thomas.lendacky@....com, x86@...nel.org, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, rientjes@...gle.com,
srutherford@...gle.com, luto@...nel.org, brijesh.singh@....com
Subject: Re: [PATCH v6 10/14] mm: x86: Invoke hypercall when page encryption
status is changed
On Fri, Apr 03, 2020 at 02:07:02PM -0700, Krish Sadhukhan wrote:
>
> On 3/29/20 11:22 PM, Ashish Kalra wrote:
> > From: Brijesh Singh <Brijesh.Singh@....com>
> >
> > Invoke a hypercall when a memory region is changed from encrypted ->
> > decrypted and vice versa. Hypervisor need to know the page encryption
> > status during the guest migration.
> >
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: "Radim Krčmář" <rkrcmar@...hat.com>
> > Cc: Joerg Roedel <joro@...tes.org>
> > Cc: Borislav Petkov <bp@...e.de>
> > Cc: Tom Lendacky <thomas.lendacky@....com>
> > Cc: x86@...nel.org
> > Cc: kvm@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> > Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> > ---
> > 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 694d8daf4983..8127b9c141bf 100644
> > --- a/arch/x86/include/asm/paravirt.h
> > +++ b/arch/x86/include/asm/paravirt.h
> > @@ -78,6 +78,12 @@ 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)
> > {
> > @@ -946,6 +952,10 @@ 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 732f62e04ddb..03bfd515c59c 100644
> > --- a/arch/x86/include/asm/paravirt_types.h
> > +++ b/arch/x86/include/asm/paravirt_types.h
> > @@ -215,6 +215,8 @@ 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 c131ba4e70ef..840c02b23aeb 100644
> > --- a/arch/x86/kernel/paravirt.c
> > +++ b/arch/x86/kernel/paravirt.c
> > @@ -367,6 +367,7 @@ 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 f4bd4b431ba1..c9800fa811f6 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"
> > @@ -196,6 +198,47 @@ void __init sme_early_init(void)
> > swiotlb_force = SWIOTLB_FORCE;
> > }
> > +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;
> > + }
>
>
> Is it possible to re-use the code in __set_clr_pte_enc() ?
>
> > +
> > + 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;
> > @@ -253,12 +296,13 @@ 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;
> > @@ -313,6 +357,8 @@ 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);
>
>
> If I haven't missed anything, it seems early_set_memory_encrypted() doesn't
> have a caller. So is there a possibility that we can end up calling it in
> non-SEV context and hence do we need to have the sev_active() guard here ?
>
As of now early_set_memory_encrypted() is not used, but
early_set_memory_decrypted() is used in __set_percpu_decrypted() and
that is called with the sev_active() check.
Thanks,
Ashish
> > out:
> > __flush_tlb_all();
> > return ret;
> > @@ -451,6 +497,15 @@ void __init mem_encrypt_init(void)
> > if (sev_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
> > +
> > pr_info("AMD %s active\n",
> > sev_active() ? "Secure Encrypted Virtualization (SEV)"
> > : "Secure Memory Encryption (SME)");
> > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> > index c4aedd00c1ba..86b7804129fc 100644
> > --- a/arch/x86/mm/pat/set_memory.c
> > +++ b/arch/x86/mm/pat/set_memory.c
> > @@ -26,6 +26,7 @@
> > #include <asm/proto.h>
> > #include <asm/memtype.h>
> > #include <asm/set_memory.h>
> > +#include <asm/paravirt.h>
> > #include "../mm_internal.h"
> > @@ -1987,6 +1988,12 @@ 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;
> > }
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