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Fri, 01 Dec 2023 09:04:52 -0800 (PST) Date: Fri, 1 Dec 2023 09:04:51 -0800 In-Reply-To: <20231123003513.24292-3-ankita@nvidia.com> Mime-Version: 1.0 References: <20231123003513.24292-1-ankita@nvidia.com> <20231123003513.24292-3-ankita@nvidia.com> Message-ID: Subject: Re: [PATCH v2 2/4] mm: Add poison error check in fixup_user_fault() for mapped pfn From: Sean Christopherson To: ankita@nvidia.com Cc: jgg@nvidia.com, alex.williamson@redhat.com, naoya.horiguchi@nec.com, akpm@linux-foundation.org, tony.luck@intel.com, bp@alien8.de, linmiaohe@huawei.com, rafael@kernel.org, lenb@kernel.org, james.morse@arm.com, shiju.jose@huawei.com, bhelgaas@google.com, pabeni@redhat.com, yishaih@nvidia.com, shameerali.kolothum.thodi@huawei.com, kevin.tian@intel.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, anuaggarwal@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, mochs@nvidia.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-edac@vger.kernel.org, linux-acpi@vger.kernel.org Content-Type: text/plain; charset="us-ascii" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 966DAC0027 X-Stat-Signature: 9g33qsf9akxyzwjk3s4ss9xpa9neygad X-Rspam-User: X-HE-Tag: 1701450293-791289 X-HE-Meta: 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 hUv04JQW 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005556, 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 Thu, Nov 23, 2023, ankita@nvidia.com wrote: > From: Ankit Agrawal > > The fixup_user_fault() currently does not expect a VM_FAULT_HWPOISON > and hence does not check for it while calling vm_fault_to_errno(). Since > we now have a new code path which can trigger such case, change > fixup_user_fault to look for VM_FAULT_HWPOISON. > > Also make hva_to_pfn_remapped check for -EHWPOISON and communicate the > poison fault up to the user_mem_abort(). I would much prefer the KVM change be split out to its own patch, I see no reason why it needs to be bundled with the fixup_user_fault() change. KVM will set pfn to KVM_PFN_ERR_FAULT before and after the fixup_user_fault() change. > Signed-off-by: Ankit Agrawal > --- > mm/gup.c | 2 +- > virt/kvm/kvm_main.c | 6 ++++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 231711efa390..b78af20a0f52 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1414,7 +1414,7 @@ int fixup_user_fault(struct mm_struct *mm, > } > > if (ret & VM_FAULT_ERROR) { > - int err = vm_fault_to_errno(ret, 0); > + int err = vm_fault_to_errno(ret, FOLL_HWPOISON); > > if (err) > return err; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 486800a7024b..2ff067f21a7c 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2731,6 +2731,12 @@ kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool interruptible, > r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn); > if (r == -EAGAIN) > goto retry; > + > + if (r == -EHWPOISON) { > + pfn = KVM_PFN_ERR_HWPOISON; > + goto exit; > + } > + > if (r < 0) > pfn = KVM_PFN_ERR_FAULT; I vote for if (r == -EHWPOISON) pfn = KVM_PFN_ERR_HWPOISON; else if (r < 0) pfn = KVM_PFN_ERR_FAULT; or even opportunstically fix the < 0 weirdness: if (r == -EHWPOISON) pfn = KVM_PFN_ERR_HWPOISON; else if (r) pfn = KVM_PFN_ERR_FAULT; It's rather confusing to see a goto in one error path but an effective fallthrough in a different error path, i.e. gives the impression that KVM_PFN_ERR_HWPOISON has some special behavior that doesn't apply to KVM_PFN_ERR_FAULT.