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Mon, 29 Jan 2024 14:26:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id BmKbJZW1t2WqNQAAD6G6ig (envelope-from ); Mon, 29 Jan 2024 14:26:29 +0000 Message-ID: <1cc76023-ef3e-4639-9a02-644c5abe918d@suse.cz> Date: Mon, 29 Jan 2024 15:26:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 15/25] x86/sev: Introduce snp leaked pages list Content-Language: en-US To: Michael Roth , x86@kernel.org Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, tobin@ibm.com, bp@alien8.de, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, pankaj.gupta@amd.com, liam.merwick@oracle.com References: <20240126041126.1927228-1-michael.roth@amd.com> <20240126041126.1927228-16-michael.roth@amd.com> From: Vlastimil Babka In-Reply-To: <20240126041126.1927228-16-michael.roth@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: CF9FF180007 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: qh9snh1m4mgxedtj1j7fa96z67nx5p4g X-HE-Tag: 1706538393-960859 X-HE-Meta: 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 JrA277FE wyjwhwLRtdPixeUT7aa/FmG+MMX4xqpy4tAKUMk4HAHwIPyr6WQkr4K7R+zdrlfY8KxiR9FU3Pf7gq85q7KRPubLDQwt15fNp6vHzFXpzY+ZS7Xhx1qdCblhns3ClZPebRp+o9AtTdO/RdHyekjnutdAXDWXBgBOJyCxypH6I3Vv6lMfzVXMRFnUf/ydCWK0BVML8vOrxBngOF80UEYrghY+g+/IoEMPzc4aLcwr9ma976e0lS7dK2WA5g7N4Gyz0K6sNFPE8jhQ8M83FBZoj1HP/k9SNZ9JxwGzuriTxNXmtHsABet9b2SZTaykQ/EMRnl4v X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/26/24 05:11, Michael Roth wrote: > From: Ashish Kalra > > Pages are unsafe to be released back to the page-allocator, if they > have been transitioned to firmware/guest state and can't be reclaimed > or transitioned back to hypervisor/shared state. In this case add > them to an internal leaked pages list to ensure that they are not freed > or touched/accessed to cause fatal page faults. > > Suggested-by: Vlastimil Babka > Signed-off-by: Ashish Kalra > [mdr: relocate to arch/x86/virt/svm/sev.c] > Signed-off-by: Michael Roth Reviewed-by: Vlastimil Babka Some minor nitpicks: > --- > arch/x86/include/asm/sev.h | 2 ++ > arch/x86/virt/svm/sev.c | 34 ++++++++++++++++++++++++++++++++++ > 2 files changed, 36 insertions(+) > > diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h > index d3ccb7a0c7e9..435ba9bc4510 100644 > --- a/arch/x86/include/asm/sev.h > +++ b/arch/x86/include/asm/sev.h > @@ -264,6 +264,7 @@ void snp_dump_hva_rmpentry(unsigned long address); > int psmash(u64 pfn); > int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable); > int rmp_make_shared(u64 pfn, enum pg_level level); > +void snp_leak_pages(u64 pfn, unsigned int npages); > #else > static inline bool snp_probe_rmptable_info(void) { return false; } > static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; } > @@ -275,6 +276,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int as > return -ENODEV; > } > static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; } > +static inline void snp_leak_pages(u64 pfn, unsigned int npages) {} > #endif > > #endif > diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c > index 1a13eff78c9d..649ac1bb6b0e 100644 > --- a/arch/x86/virt/svm/sev.c > +++ b/arch/x86/virt/svm/sev.c > @@ -65,6 +65,11 @@ static u64 probed_rmp_base, probed_rmp_size; > static struct rmpentry *rmptable __ro_after_init; > static u64 rmptable_max_pfn __ro_after_init; > > +static LIST_HEAD(snp_leaked_pages_list); > +static DEFINE_SPINLOCK(snp_leaked_pages_list_lock); > + > +static unsigned long snp_nr_leaked_pages; > + > #undef pr_fmt > #define pr_fmt(fmt) "SEV-SNP: " fmt > > @@ -505,3 +510,32 @@ int rmp_make_shared(u64 pfn, enum pg_level level) > return rmpupdate(pfn, &state); > } > EXPORT_SYMBOL_GPL(rmp_make_shared); > + > +void snp_leak_pages(u64 pfn, unsigned int npages) > +{ > + struct page *page = pfn_to_page(pfn); > + > + pr_warn("Leaking PFN range 0x%llx-0x%llx\n", pfn, pfn + npages); > + > + spin_lock(&snp_leaked_pages_list_lock); > + while (npages--) { > + /* > + * Reuse the page's buddy list for chaining into the leaked > + * pages list. This page should not be on a free list currently > + * and is also unsafe to be added to a free list. > + */ > + if (likely(!PageCompound(page)) || > + (PageHead(page) && compound_nr(page) <= npages)) > + /* > + * Skip inserting tail pages of compound page as > + * page->buddy_list of tail pages is not usable. > + */ > + list_add_tail(&page->buddy_list, &snp_leaked_pages_list); Even though it's not necessary for correctness, with the comment I'd put the whole block into { } to make easier to follow. Or just move the comment above the if() itself? > + dump_rmpentry(pfn); > + snp_nr_leaked_pages++; > + pfn++; > + page++; > + } > + spin_unlock(&snp_leaked_pages_list_lock); > +} > +EXPORT_SYMBOL_GPL(snp_leak_pages);