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Message-ID: <20210413010103.GA3214@ashkalra_ubuntu_server>
Date: Tue, 13 Apr 2021 01:01:03 +0000
From: Ashish Kalra <ashish.kalra@....com>
To: Steve Rutherford <srutherford@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
Borislav Petkov <bp@...e.de>,
Tom Lendacky <thomas.lendacky@....com>,
X86 ML <x86@...nel.org>, KVM list <kvm@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Sean Christopherson <seanjc@...gle.com>,
Venu Busireddy <venu.busireddy@...cle.com>,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v12 12/13] x86/kvm: Add guest support for detecting and
enabling SEV Live Migration feature.
On Mon, Apr 12, 2021 at 05:25:15PM -0700, Steve Rutherford wrote:
> On Mon, Apr 12, 2021 at 12:46 PM Ashish Kalra <Ashish.Kalra@....com> wrote:
> >
> > From: Ashish Kalra <ashish.kalra@....com>
> >
> > The guest support for detecting and enabling SEV Live migration
> > feature uses the following logic :
> >
> > - kvm_init_plaform() invokes check_kvm_sev_migration() which
> > checks if its booted under the EFI
> >
> > - If not EFI,
> >
> > i) check for the KVM_FEATURE_CPUID
> >
> > ii) if CPUID reports that migration is supported, issue a wrmsrl()
> > to enable the SEV live migration support
> >
> > - If EFI,
> >
> > i) check for the KVM_FEATURE_CPUID
> >
> > ii) If CPUID reports that migration is supported, read the UEFI variable which
> > indicates OVMF support for live migration
> >
> > iii) the variable indicates live migration is supported, issue a wrmsrl() to
> > enable the SEV live migration support
> >
> > The EFI live migration check is done using a late_initcall() callback.
> >
> > Also, ensure that _bss_decrypted section is marked as decrypted in the
> > shared pages list.
> >
> > Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> > ---
> > arch/x86/include/asm/mem_encrypt.h | 8 +++++
> > arch/x86/kernel/kvm.c | 52 ++++++++++++++++++++++++++++++
> > arch/x86/mm/mem_encrypt.c | 41 +++++++++++++++++++++++
> > 3 files changed, 101 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> > index 31c4df123aa0..19b77f3a62dc 100644
> > --- a/arch/x86/include/asm/mem_encrypt.h
> > +++ b/arch/x86/include/asm/mem_encrypt.h
> > @@ -21,6 +21,7 @@
> > extern u64 sme_me_mask;
> > extern u64 sev_status;
> > extern bool sev_enabled;
> > +extern bool sev_live_migration_enabled;
> >
> > void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
> > unsigned long decrypted_kernel_vaddr,
> > @@ -44,8 +45,11 @@ void __init sme_enable(struct boot_params *bp);
> >
> > int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
> > int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
> > +void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
> > + bool enc);
> >
> > void __init mem_encrypt_free_decrypted_mem(void);
> > +void __init check_kvm_sev_migration(void);
> >
> > /* Architecture __weak replacement functions */
> > void __init mem_encrypt_init(void);
> > @@ -60,6 +64,7 @@ bool sev_es_active(void);
> > #else /* !CONFIG_AMD_MEM_ENCRYPT */
> >
> > #define sme_me_mask 0ULL
> > +#define sev_live_migration_enabled false
> >
> > static inline void __init sme_early_encrypt(resource_size_t paddr,
> > unsigned long size) { }
> > @@ -84,8 +89,11 @@ static inline int __init
> > early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
> > static inline int __init
> > early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
> > +static inline void __init
> > +early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc) {}
> >
> > static inline void mem_encrypt_free_decrypted_mem(void) { }
> > +static inline void check_kvm_sev_migration(void) { }
> >
> > #define __bss_decrypted
> >
> > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> > index 78bb0fae3982..bcc82e0c9779 100644
> > --- a/arch/x86/kernel/kvm.c
> > +++ b/arch/x86/kernel/kvm.c
> > @@ -26,6 +26,7 @@
> > #include <linux/kprobes.h>
> > #include <linux/nmi.h>
> > #include <linux/swait.h>
> > +#include <linux/efi.h>
> > #include <asm/timer.h>
> > #include <asm/cpu.h>
> > #include <asm/traps.h>
> > @@ -429,6 +430,56 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
> > early_set_memory_decrypted((unsigned long) ptr, size);
> > }
> >
> > +static int __init setup_kvm_sev_migration(void)
> > +{
> > + efi_char16_t efi_sev_live_migration_enabled[] = L"SevLiveMigrationEnabled";
> > + efi_guid_t efi_variable_guid = MEM_ENCRYPT_GUID;
> > + efi_status_t status;
> > + unsigned long size;
> > + bool enabled;
> > +
> > + /*
> > + * check_kvm_sev_migration() invoked via kvm_init_platform() before
> > + * this callback would have setup the indicator that live migration
> > + * feature is supported/enabled.
> > + */
> > + if (!sev_live_migration_enabled)
> > + return 0;
> > +
> > + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> > + pr_info("%s : EFI runtime services are not enabled\n", __func__);
> > + return 0;
> > + }
> > +
> > + size = sizeof(enabled);
> > +
> > + /* Get variable contents into buffer */
> > + status = efi.get_variable(efi_sev_live_migration_enabled,
> > + &efi_variable_guid, NULL, &size, &enabled);
> > +
> > + if (status == EFI_NOT_FOUND) {
> > + pr_info("%s : EFI live migration variable not found\n", __func__);
> > + return 0;
> > + }
> > +
> > + if (status != EFI_SUCCESS) {
> > + pr_info("%s : EFI variable retrieval failed\n", __func__);
> > + return 0;
> > + }
> > +
> > + if (enabled == 0) {
> > + pr_info("%s: live migration disabled in EFI\n", __func__);
> > + return 0;
> > + }
> > +
> > + pr_info("%s : live migration enabled in EFI\n", __func__);
> > + wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION, KVM_SEV_LIVE_MIGRATION_ENABLED);
> > +
> > + return true;
> > +}
> > +
> > +late_initcall(setup_kvm_sev_migration);
> > +
> > /*
> > * Iterate through all possible CPUs and map the memory region pointed
> > * by apf_reason, steal_time and kvm_apic_eoi as decrypted at once.
> > @@ -747,6 +798,7 @@ static bool __init kvm_msi_ext_dest_id(void)
> >
> > static void __init kvm_init_platform(void)
> > {
> > + check_kvm_sev_migration();
> > kvmclock_init();
> > x86_platform.apic_post_init = kvm_apic_init;
> > }
> > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> > index fae9ccbd0da7..4de417333c09 100644
> > --- a/arch/x86/mm/mem_encrypt.c
> > +++ b/arch/x86/mm/mem_encrypt.c
> > @@ -20,6 +20,7 @@
> > #include <linux/bitops.h>
> > #include <linux/dma-mapping.h>
> > #include <linux/kvm_para.h>
> > +#include <linux/efi.h>
> >
> > #include <asm/tlbflush.h>
> > #include <asm/fixmap.h>
> > @@ -48,6 +49,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
> >
> > bool sev_enabled __section(".data");
> >
> > +bool sev_live_migration_enabled __section(".data");
> > +
> > /* Buffer used for early in-place encryption by BSP, no locking needed */
> > static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
> >
> > @@ -237,6 +240,9 @@ static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
> > unsigned long sz = npages << PAGE_SHIFT;
> > unsigned long vaddr_end, vaddr_next;
> >
> > + if (!sev_live_migration_enabled)
> > + return;
> > +
> > vaddr_end = vaddr + sz;
> >
> > for (; vaddr < vaddr_end; vaddr = vaddr_next) {
> > @@ -407,6 +413,12 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
> > return early_set_memory_enc_dec(vaddr, size, true);
> > }
> >
> > +void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
> > + bool enc)
> > +{
> > + set_memory_enc_dec_hypercall(vaddr, npages, enc);
> > +}
> > +
> > /*
> > * SME and SEV are very similar but they are not the same, so there are
> > * times that the kernel will need to distinguish between SME and SEV. The
> > @@ -462,6 +474,35 @@ bool force_dma_unencrypted(struct device *dev)
> > return false;
> > }
> >
> > +void __init check_kvm_sev_migration(void)
> > +{
> > + if (sev_active() &&
> > + kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
> > + unsigned long nr_pages;
> > +
> > + pr_info("KVM enable live migration\n");
> > + sev_live_migration_enabled = true;
> > +
> > + /*
> > + * Ensure that _bss_decrypted section is marked as decrypted in the
> > + * shared pages list.
> > + */
> > + nr_pages = DIV_ROUND_UP(__end_bss_decrypted - __start_bss_decrypted,
> > + PAGE_SIZE);
> > + early_set_mem_enc_dec_hypercall((unsigned long)__start_bss_decrypted,
> > + nr_pages, 0);
> > +
> > + /*
> > + * If not booted using EFI, enable Live migration support.
> > + */
> > + if (!efi_enabled(EFI_BOOT))
> > + wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
> > + KVM_SEV_LIVE_MIGRATION_ENABLED);
> > + } else {
> > + pr_info("KVM enable live migration feature unsupported\n");
> I might be misunderstanding this, but I'm not sure this log message is
> correct: isn't the intention that the late initcall will be the one to
> check if this should be enabled later in this case?
>
Yes, you are right, this log message should be removed.
> I have a similar question above about the log message after
> "!efi_enabled(EFI_RUNTIME_SERVICES)": shouldn't that avoid logging if
> !efi_enabled(EFI_BOOT) (since the wrmsl call already had been made
> here?)
Yes, probably that check can be additionally added.
Thanks,
Ashish
> > + }
> > +}
> > +
> > void __init mem_encrypt_free_decrypted_mem(void)
> > {
> > unsigned long vaddr, vaddr_end, npages;
> > --
> > 2.17.1
> >
>
> Other than these:
> Reviewed-by: Steve Rutherford <srutherford@...gle.com>
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