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Message-ID: <CAMj1kXH5C6FzMyrki_23TTk_Yma5NJdHTo-nv4DmZoz_qaGbVQ@mail.gmail.com>
Date: Tue, 13 May 2025 14:55:40 +0100
From: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org, x86@...nel.org,
Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
Dionna Amalie Glaze <dionnaglaze@...gle.com>, Kevin Loughlin <kevinloughlin@...gle.com>,
Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFT PATCH v3 09/21] x86/sev: Pass SVSM calling area down to
early page state change API
On Mon, 12 May 2025 at 20:11, Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> From: Ard Biesheuvel <ardb@...nel.org>
>
> The early page state change API is mostly only used very early, when
> only the boot time SVSM calling area is in use. However, this API is
> also called by the kexec finishing code, which runs very late, and
> potentially from a different CPU (which uses a different calling area).
>
> To avoid pulling the per-CPU SVSM calling area pointers and related SEV
> state into the startup code, refactor the page state change API so the
> SVSM calling area virtual and physical addresses can be provided by the
> caller.
>
> No functional change intended.
>
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
This patch is broken - I'll send a followup fix asap.
> ---
> arch/x86/boot/compressed/sev.c | 12 +++++++++---
> arch/x86/boot/startup/sev-shared.c | 18 ++++++++++--------
> arch/x86/boot/startup/sev-startup.c | 11 +++++++----
> arch/x86/coco/sev/core.c | 3 ++-
> arch/x86/include/asm/sev-internal.h | 3 ++-
> 5 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 7a01eef9ae01..04bc39d065ff 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -68,7 +68,9 @@ void snp_set_page_private(unsigned long paddr)
> return;
>
> msr = sev_es_rd_ghcb_msr();
> - __page_state_change(paddr, SNP_PAGE_STATE_PRIVATE);
> + __page_state_change(paddr, SNP_PAGE_STATE_PRIVATE,
> + (struct svsm_ca *)boot_svsm_caa_pa,
> + boot_svsm_caa_pa);
> sev_es_wr_ghcb_msr(msr);
> }
>
> @@ -80,7 +82,9 @@ void snp_set_page_shared(unsigned long paddr)
> return;
>
> msr = sev_es_rd_ghcb_msr();
> - __page_state_change(paddr, SNP_PAGE_STATE_SHARED);
> + __page_state_change(paddr, SNP_PAGE_STATE_SHARED,
> + (struct svsm_ca *)boot_svsm_caa_pa,
> + boot_svsm_caa_pa);
> sev_es_wr_ghcb_msr(msr);
> }
>
> @@ -109,7 +113,9 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
> u64 msr = sev_es_rd_ghcb_msr();
>
> for (phys_addr_t pa = start; pa < end; pa += PAGE_SIZE)
> - __page_state_change(pa, SNP_PAGE_STATE_PRIVATE);
> + __page_state_change(pa, SNP_PAGE_STATE_PRIVATE,
> + (struct svsm_ca *)boot_svsm_caa_pa,
> + boot_svsm_caa_pa);
> sev_es_wr_ghcb_msr(msr);
> }
>
> diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
> index dae770327b50..70ad9a0aa023 100644
> --- a/arch/x86/boot/startup/sev-shared.c
> +++ b/arch/x86/boot/startup/sev-shared.c
> @@ -538,7 +538,8 @@ static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
> }
> }
>
> -static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
> +static void __head svsm_pval_4k_page(unsigned long paddr, bool validate,
> + struct svsm_ca *caa, u64 caa_pa)
> {
> struct svsm_pvalidate_call *pc;
> struct svsm_call call = {};
> @@ -552,10 +553,10 @@ static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
> */
> flags = native_local_irq_save();
>
> - call.caa = svsm_get_caa();
> + call.caa = caa;
>
> pc = (struct svsm_pvalidate_call *)call.caa->svsm_buffer;
> - pc_pa = svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
> + pc_pa = caa_pa + offsetof(struct svsm_ca, svsm_buffer);
>
> pc->num_entries = 1;
> pc->cur_index = 0;
> @@ -578,12 +579,12 @@ static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
> }
>
> static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
> - bool validate)
> + bool validate, struct svsm_ca *caa, u64 caa_pa)
> {
> int ret;
>
> if (snp_vmpl) {
> - svsm_pval_4k_page(paddr, validate);
> + svsm_pval_4k_page(paddr, validate, caa, caa_pa);
> } else {
> ret = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
> if (ret)
> @@ -591,7 +592,8 @@ static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
> }
> }
>
> -static void __head __page_state_change(unsigned long paddr, enum psc_op op)
> +static void __head __page_state_change(unsigned long paddr, enum psc_op op,
> + struct svsm_ca *caa, u64 caa_pa)
> {
> u64 val;
>
> @@ -600,7 +602,7 @@ static void __head __page_state_change(unsigned long paddr, enum psc_op op)
> * state change in the RMP table.
> */
> if (op == SNP_PAGE_STATE_SHARED)
> - pvalidate_4k_page(paddr, paddr, false);
> + pvalidate_4k_page(paddr, paddr, false, caa, caa_pa);
>
> /* Issue VMGEXIT to change the page state in RMP table. */
> sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
> @@ -616,7 +618,7 @@ static void __head __page_state_change(unsigned long paddr, enum psc_op op)
> * consistent with the RMP entry.
> */
> if (op == SNP_PAGE_STATE_PRIVATE)
> - pvalidate_4k_page(paddr, paddr, true);
> + pvalidate_4k_page(paddr, paddr, true, caa, caa_pa);
> }
>
> /*
> diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
> index 28bf68753580..7a3ad17d06f6 100644
> --- a/arch/x86/boot/startup/sev-startup.c
> +++ b/arch/x86/boot/startup/sev-startup.c
> @@ -132,7 +132,8 @@ noinstr void __sev_put_ghcb(struct ghcb_state *state)
>
> void __head
> early_set_pages_state(unsigned long vaddr, unsigned long paddr,
> - unsigned long npages, enum psc_op op)
> + unsigned long npages, enum psc_op op,
> + struct svsm_ca *caa, u64 caa_pa)
> {
> unsigned long paddr_end;
>
> @@ -142,7 +143,7 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
> paddr_end = paddr + (npages << PAGE_SHIFT);
>
> while (paddr < paddr_end) {
> - __page_state_change(paddr, op);
> + __page_state_change(paddr, op, caa, caa_pa);
>
> vaddr += PAGE_SIZE;
> paddr += PAGE_SIZE;
> @@ -165,7 +166,8 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
> * Ask the hypervisor to mark the memory pages as private in the RMP
> * table.
> */
> - early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_PRIVATE);
> + early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_PRIVATE,
> + svsm_get_caa(), svsm_get_caa_pa());
> }
>
> void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
> @@ -181,7 +183,8 @@ void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr
> return;
>
> /* Ask hypervisor to mark the memory pages shared in the RMP table. */
> - early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_SHARED);
> + early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_SHARED,
> + svsm_get_caa(), svsm_get_caa_pa());
> }
>
> /*
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index 0e0ddf4c92aa..39bbbea09c24 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -584,7 +584,8 @@ static void set_pages_state(unsigned long vaddr, unsigned long npages, int op)
>
> /* Use the MSR protocol when a GHCB is not available. */
> if (!boot_ghcb)
> - return early_set_pages_state(vaddr, __pa(vaddr), npages, op);
> + return early_set_pages_state(vaddr, __pa(vaddr), npages, op,
> + svsm_get_caa(), svsm_get_caa_pa());
>
> vaddr = vaddr & PAGE_MASK;
> vaddr_end = vaddr + (npages << PAGE_SHIFT);
> diff --git a/arch/x86/include/asm/sev-internal.h b/arch/x86/include/asm/sev-internal.h
> index e3b203c280aa..08e2cfdef512 100644
> --- a/arch/x86/include/asm/sev-internal.h
> +++ b/arch/x86/include/asm/sev-internal.h
> @@ -55,7 +55,8 @@ DECLARE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
> DECLARE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
>
> void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
> - unsigned long npages, enum psc_op op);
> + unsigned long npages, enum psc_op op,
> + struct svsm_ca *ca, u64 caa_pa);
>
> DECLARE_PER_CPU(struct svsm_ca *, svsm_caa);
> DECLARE_PER_CPU(u64, svsm_caa_pa);
> --
> 2.49.0.1045.g170613ef41-goog
>
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