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Thu, 23 Jul 2026 00:17:25 -0700 (PDT) Message-ID: <3114b501-158f-46f5-b999-68b5896aa3f8@suse.com> Date: Thu, 23 Jul 2026 10:17:22 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 08/11] KVM: TDX: Get/put PAMT pages when (un)mapping private memory To: Sean Christopherson , Rick P Edgecombe Cc: "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , Kai Huang , Dave Hansen , Yan Y Zhao , "tony.lindgren@linux.intel.com" , Binbin Wu , "kas@kernel.org" , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , "pbonzini@redhat.com" , "linux-doc@vger.kernel.org" , "hpa@zytor.com" , "tglx@kernel.org" , Vishal Annapurve , "bp@alien8.de" , Chao Gao , "x86@kernel.org" , "binbin.wu@linux.intel.com" References: <20260718014500.2231262-1-rick.p.edgecombe@intel.com> <20260718014500.2231262-9-rick.p.edgecombe@intel.com> <20900cd6-6d05-4a20-a21d-2a1d4a6ef5e5@suse.com> <4ad035a82ee10dc4645e26a4bd1daf40786a743a.camel@intel.com> From: Nikolay Borisov Content-Language: en-US Autocrypt: addr=nik.borisov@suse.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/22/26 22:34, Sean Christopherson wrote: > On Wed, Jul 22, 2026, Rick P Edgecombe wrote: >> On Wed, 2026-07-22 at 16:46 +0300, Nikolay Borisov wrote: >>>> +static int tdx_topup_external_pamt_cache(struct kvm_vcpu *vcpu, int >>>> min_nr_spts) >>>> +{ >>>> + /* >>>> + * Don't cover the root SPT, but cover a possible 4KB private >>>> + * page in addition to the SPTs. So -1 to exclude the root >>>> + * SPT, and +1 for the guest page cancel out. >>>> + */ >>> >>> That comment here doesn't seem to correspond to the code in anyway. >>> There are no +-1 adjustments. >> >> The +1 and -1 cancel each other out. Hmm, how about: >> /* >> * Don't cover the root SPT, but cover a possible 4KB private >> * page in addition to the SPTs. The -1 to exclude the root >> * SPT and +1 for the guest page cancel each other out. So >> * make no adjustments. >> */ > > Maybe put it in code? E.g. > > /* > * Minus one page to exclude the root SPT, but plus one page for a > * possible 4KiB private mapping. > */ > min_nr_spts += -1 + 1; Makes sense > > return tdx_topup_pamt_cache(&to_tdx(vcpu)->pamt_cache, min_nr_spts);