From: Borislav Petkov <bp@alien8.de>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, linux-efi@vger.kernel.org,
platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, linux-crypto@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Michael Roth <michael.roth@amd.com>,
Vlastimil Babka <vbabka@suse.cz>,
tony.luck@intel.com, npmccallum@redhat.com,
brijesh.ksingh@gmail.com
Subject: Re: [PATCH Part1 RFC v4 15/36] x86/mm: Add support to validate memory when changing C-bit
Date: Tue, 17 Aug 2021 19:27:02 +0200 [thread overview]
Message-ID: <YRvxZtLkVNda9xwX@zn.tnic> (raw)
In-Reply-To: <20210707181506.30489-16-brijesh.singh@amd.com>
On Wed, Jul 07, 2021 at 01:14:45PM -0500, Brijesh Singh wrote:
> +struct __packed psc_hdr {
> + u16 cur_entry;
> + u16 end_entry;
> + u32 reserved;
> +};
> +
> +struct __packed psc_entry {
> + u64 cur_page : 12,
> + gfn : 40,
> + operation : 4,
> + pagesize : 1,
> + reserved : 7;
> +};
> +
> +struct __packed snp_psc_desc {
> + struct psc_hdr hdr;
> + struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];
> +};
The majority of kernel code puts __packed after the struct definition,
let's put it there too pls, out of the way.
...
> +static int vmgexit_psc(struct snp_psc_desc *desc)
> +{
> + int cur_entry, end_entry, ret;
> + struct snp_psc_desc *data;
> + struct ghcb_state state;
> + struct ghcb *ghcb;
> + struct psc_hdr *hdr;
> + unsigned long flags;
> +
> + local_irq_save(flags);
> +
> + ghcb = __sev_get_ghcb(&state);
> + if (unlikely(!ghcb))
> + panic("SEV-SNP: Failed to get GHCB\n");
> +
> + /* Copy the input desc into GHCB shared buffer */
> + data = (struct snp_psc_desc *)ghcb->shared_buffer;
> + memcpy(ghcb->shared_buffer, desc, sizeof(*desc));
> +
> + hdr = &data->hdr;
> + cur_entry = hdr->cur_entry;
> + end_entry = hdr->end_entry;
> +
> + /*
> + * As per the GHCB specification, the hypervisor can resume the guest
> + * before processing all the entries. Checks whether all the entries
> + * are processed. If not, then keep retrying.
> + *
> + * The stragtegy here is to wait for the hypervisor to change the page
> + * state in the RMP table before guest access the memory pages. If the
> + * page state was not successful, then later memory access will result
> + * in the crash.
> + */
> + while (hdr->cur_entry <= hdr->end_entry) {
> + ghcb_set_sw_scratch(ghcb, (u64)__pa(data));
> +
> + ret = sev_es_ghcb_hv_call(ghcb, NULL, SVM_VMGEXIT_PSC, 0, 0);
> +
> + /*
> + * Page State Change VMGEXIT can pass error code through
> + * exit_info_2.
> + */
> + if (WARN(ret || ghcb->save.sw_exit_info_2,
> + "SEV-SNP: page state change failed ret=%d exit_info_2=%llx\n",
> + ret, ghcb->save.sw_exit_info_2))
> + return 1;
Yikes, you return here and below with interrupts disabled.
All your returns need to be "goto out;" instead where you do
out:
__sev_put_ghcb(&state);
local_irq_restore(flags);
Yap, you very likely need to put the GHCB too.
> + /*
> + * Lets do some sanity check that entry processing is not going
> + * backward. This will happen only if hypervisor is tricking us.
> + */
> + if (WARN((hdr->end_entry > end_entry) || (cur_entry > hdr->cur_entry),
> + "SEV-SNP: page state change processing going backward, end_entry "
> + "(expected %d got %d) cur_entry (expected %d got %d)\n",
> + end_entry, hdr->end_entry, cur_entry, hdr->cur_entry))
> + return 1;
WARNING: quoted string split across lines
#293: FILE: arch/x86/kernel/sev.c:750:
+ "SEV-SNP: page state change processing going backward, end_entry "
+ "(expected %d got %d) cur_entry (expected %d got %d)\n",
If you're wondering what to do, yes, you can really stretch that string
and shorten it too:
if (WARN((hdr->end_entry > end_entry) || (cur_entry > hdr->cur_entry),
"SEV-SNP: PSC processing going backwards, end_entry %d (got %d) cur_entry: %d (got %d)\n",
end_entry, hdr->end_entry, cur_entry, hdr->cur_entry))
return 1;
so that it fits on a single line and grepping can find it.
> + /* Lets verify that reserved bit is not set in the header*/
> + if (WARN(hdr->reserved, "Reserved bit is set in the PSC header\n"))
psc_entry has a ->reserved field too and since we're iterating over the
entries...
> + return 1;
> + }
> +
> + __sev_put_ghcb(&state);
> + local_irq_restore(flags);
> +
> + return 0;
> +}
> +
> +static void __set_page_state(struct snp_psc_desc *data, unsigned long vaddr,
> + unsigned long vaddr_end, int op)
> +{
> + struct psc_hdr *hdr;
> + struct psc_entry *e;
> + unsigned long pfn;
> + int i;
> +
> + hdr = &data->hdr;
> + e = data->entries;
> +
> + memset(data, 0, sizeof(*data));
> + i = 0;
> +
> + while (vaddr < vaddr_end) {
> + if (is_vmalloc_addr((void *)vaddr))
> + pfn = vmalloc_to_pfn((void *)vaddr);
> + else
> + pfn = __pa(vaddr) >> PAGE_SHIFT;
> +
> + e->gfn = pfn;
> + e->operation = op;
> + hdr->end_entry = i;
> +
> + /*
> + * The GHCB specification provides the flexibility to
> + * use either 4K or 2MB page size in the RMP table.
> + * The current SNP support does not keep track of the
> + * page size used in the RMP table. To avoid the
> + * overlap request, use the 4K page size in the RMP
> + * table.
> + */
> + e->pagesize = RMP_PG_SIZE_4K;
> +
> + vaddr = vaddr + PAGE_SIZE;
> + e++;
> + i++;
> + }
> +
> + /* Terminate the guest on page state change failure. */
That comment is kinda obvious :)
> + if (vmgexit_psc(data))
> + sev_es_terminate(1, GHCB_TERM_PSC);
> +}
> +
> +static void set_page_state(unsigned long vaddr, unsigned int npages, int op)
> +{
> + unsigned long vaddr_end, next_vaddr;
> + struct snp_psc_desc *desc;
> +
> + vaddr = vaddr & PAGE_MASK;
> + vaddr_end = vaddr + (npages << PAGE_SHIFT);
> +
> + desc = kmalloc(sizeof(*desc), GFP_KERNEL_ACCOUNT);
kzalloc() so that you don't have to memset() later in
__set_page_state().
> + if (!desc)
> + panic("failed to allocate memory");
Make that error message more distinctive so that *if* it happens, one
can pinpoint the place in the code where the panic comes from.
> + while (vaddr < vaddr_end) {
> + /*
> + * Calculate the last vaddr that can be fit in one
> + * struct snp_psc_desc.
> + */
> + next_vaddr = min_t(unsigned long, vaddr_end,
> + (VMGEXIT_PSC_MAX_ENTRY * PAGE_SIZE) + vaddr);
> +
> + __set_page_state(desc, vaddr, next_vaddr, op);
> +
> + vaddr = next_vaddr;
> + }
> +
> + kfree(desc);
> +}
> +
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-08-17 17:26 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 18:14 [PATCH Part1 RFC v4 00/36] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 01/36] x86/sev: shorten GHCB terminate macro names Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 02/36] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-08-10 9:17 ` Borislav Petkov
2021-08-10 13:15 ` Brijesh Singh
2021-08-10 10:01 ` Borislav Petkov
2021-08-10 13:17 ` Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 03/36] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-08-10 11:22 ` Borislav Petkov
2021-08-10 13:39 ` Brijesh Singh
2021-08-10 14:03 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 04/36] x86/mm: Add sev_feature_enabled() helper Brijesh Singh
2021-07-08 8:50 ` Dr. David Alan Gilbert
2021-07-08 8:53 ` Paolo Bonzini
2021-08-10 11:25 ` Borislav Petkov
2021-08-10 14:57 ` Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 05/36] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2021-08-10 11:33 ` Borislav Petkov
2021-08-10 14:59 ` Brijesh Singh
2021-08-10 19:30 ` Tom Lendacky
2021-08-10 21:52 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 06/36] x86/sev: check SEV-SNP features support Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 07/36] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 08/36] x86/sev: check the vmpl level Brijesh Singh
2021-08-13 7:25 ` Borislav Petkov
2021-08-13 13:13 ` Brijesh Singh
2021-08-13 15:16 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 09/36] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-08-13 10:22 ` Borislav Petkov
2021-08-13 14:21 ` Brijesh Singh
2021-08-13 15:19 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 10/36] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-08-13 10:47 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 11/36] x86/sev: " Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 12/36] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-08-13 11:13 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 13/36] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-08-13 17:09 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 14/36] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 15/36] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-08-17 17:27 ` Borislav Petkov [this message]
2021-08-17 18:07 ` Brijesh Singh
2021-08-17 18:17 ` Borislav Petkov
2021-08-17 18:18 ` Brijesh Singh
2021-08-17 20:34 ` Brijesh Singh
2021-08-17 20:44 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 16/36] KVM: SVM: define new SEV_FEATURES field in the VMCB Save State Area Brijesh Singh
2021-08-17 17:54 ` Borislav Petkov
2021-08-17 17:59 ` Borislav Petkov
2021-08-17 18:11 ` Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 17/36] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 18/36] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 19/36] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 20/36] x86/sev: Use SEV-SNP AP creation to start secondary CPUs Brijesh Singh
2021-08-17 20:04 ` Borislav Petkov
2021-08-17 22:13 ` Tom Lendacky
2021-08-18 8:38 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 21/36] x86/head/64: set up a startup %gs for stack protector Brijesh Singh
2021-08-19 9:34 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 22/36] x86/sev: move MSR-based VMGEXITs for CPUID to helper Brijesh Singh
2021-08-19 9:45 ` Borislav Petkov
2021-08-19 15:37 ` Michael Roth
2021-08-19 16:46 ` Borislav Petkov
2021-08-20 3:29 ` Michael Roth
2021-08-23 4:50 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 23/36] KVM: x86: move lookup of indexed CPUID leafs " Brijesh Singh
2021-08-19 10:07 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 24/36] x86/compressed/acpi: move EFI config table access to common code Brijesh Singh
2021-08-19 10:47 ` Borislav Petkov
2021-08-19 14:58 ` Michael Roth
2021-08-19 17:09 ` Borislav Petkov
2021-08-19 23:42 ` Michael Roth
2021-08-23 4:52 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 25/36] x86/boot: Add Confidential Computing type to setup_data Brijesh Singh
2021-08-19 11:06 ` Borislav Petkov
2021-07-07 18:14 ` [PATCH Part1 RFC v4 26/36] x86/compressed/64: enable SEV-SNP-validated CPUID in #VC handler Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 27/36] x86/boot: add a pointer to Confidential Computing blob in bootparams Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 28/36] x86/compressed/64: store Confidential Computing blob address " Brijesh Singh
2021-07-07 18:14 ` [PATCH Part1 RFC v4 29/36] x86/compressed/64: add identity mapping for Confidential Computing blob Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 30/36] x86/sev: enable SEV-SNP-validated CPUID in #VC handlers Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 31/36] x86/sev: Provide support for SNP guest request NAEs Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 32/36] x86/sev: Add snp_msg_seqno() helper Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 33/36] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 34/36] virt: Add SEV-SNP guest driver Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 35/36] virt: sevguest: Add support to derive key Brijesh Singh
2021-07-07 18:15 ` [PATCH Part1 RFC v4 36/36] virt: sevguest: Add support to get extended report Brijesh Singh
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