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AJvYcCWlsXdvA+fUz5/K8deMto8RF3aiHvosRUbvt2mVDZsCaWPYzpx34fp4v05xTuTmWEHeb6Dn31WJpA==@kvack.org X-Gm-Message-State: AOJu0YwD3wP5AuYpwEDJZGcdeNErlwFLrf6n9E9fVZkaEE15N49+4wVF XwGSdCbD0LXFGXCaqxCE+GAqHKLbovTPDRiIIXSNxtbUGW0mTKVVpDnU892N9O6txtLkobjGUPp sQIXtbBrULHZSII6dOVy++lPwXqeGa+a40ExK X-Gm-Gg: ASbGncvLzMfCenkZqqzselWqTIienetz3WXpAOpOAvQqfVkWXSkwipJRDtgmvQ52QHS n0C+Oz1BQAVslNIMu7ZKxkqykIDMuP9sKr1TTwi7dg9Dd9HyOw98ho6+qkv2Dsew/nP42bF5/cM m2mDtfOIfGWOh17xPj2ruqvcdM9lo= X-Google-Smtp-Source: AGHT+IFuGLNJg10PJmFyoMKxrkIonv996LbUX7yfBM5xz7c59TtQ3nYDUZg66MCfuS/IvA1cbLhSC9h3m87uDT1cJ1M= X-Received: by 2002:ac8:5b8d:0:b0:465:c590:ed18 with SMTP id d75a77b69052e-47177e86974mr6092741cf.9.1739186166382; Mon, 10 Feb 2025 03:16:06 -0800 (PST) MIME-Version: 1.0 References: <20250206044346.3810242-1-riel@surriel.com> <20250206044346.3810242-4-riel@surriel.com> <1edea8a714fd1df0734f7fe15bb690e4c3a556dc.camel@surriel.com> In-Reply-To: <1edea8a714fd1df0734f7fe15bb690e4c3a556dc.camel@surriel.com> From: Brendan Jackman Date: Mon, 10 Feb 2025 12:15:55 +0100 X-Gm-Features: AWEUYZn3hWD36MO2gHjHYtpqDqJsgNmHP_6nAhOej5-G6whc4kZ0wQRZaGCn3mg Message-ID: Subject: Re: [PATCH v9 03/12] x86/mm: consolidate full flush threshold decision To: Rik van Riel Cc: x86@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com, Dave Hansen Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: sqmzb18eqose6go71pd5ceqqspup83jd X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 73ECF4000D X-Rspam-User: X-HE-Tag: 1739186167-243026 X-HE-Meta: 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 GJSi9HUJ 2pMPsM8cDLCg3i1lqxkVUE/qzTkmdAwnx+U+QkjnRz+66fHav+iCRREUPkQqy2U/3in7L6AvoR52XQOL4C7xEjrnDAkgdAZa30Q4jVTq+oCgTixkGpZI2vYOagOTK/LeuXmTCa8IQFhTgT1+MwVSIBEvF8z43UkT5CnTrWK85T7DJn2KN5mFvniEutTRgzeLJPXoI1QR98pMSP/p7MW7/iabhvHrKLWUK2zn2DurxvZXSzYG6CaCmdH8iY7SE1s+Fa7DWjCZDERIvDBLSfCyS1sv7VmEaI3jG/6aJMsobuz/q4LtKoKuEYirP2JuhazVbkpyHEDyzcBDYc7A= X-Bogosity: Ham, tests=bogofilter, spamicity=0.019285, 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 Fri, 7 Feb 2025 at 21:25, Rik van Riel wrote: > > On Fri, 2025-02-07 at 15:50 +0100, Brendan Jackman wrote: > > On Thu, 6 Feb 2025 at 05:45, Rik van Riel wrote: > > > @@ -1276,7 +1282,7 @@ void arch_tlbbatch_flush(struct > > > arch_tlbflush_unmap_batch *batch) > > > > > > int cpu = get_cpu(); > > > > > > - info = get_flush_tlb_info(NULL, 0, TLB_FLUSH_ALL, 0, false, > > > + info = get_flush_tlb_info(NULL, 0, TLB_FLUSH_ALL, > > > PAGE_SHIFT, false, > > > TLB_GENERATION_INVALID); > > > > [Why] do we need this change? If it's necessary here, why isn't it > > needed everywhere else that does TLB_FLUSH_ALL too, like > > flush_tlb_mm()? > > > flush_tlb_mm() calls flush_tlb_mm_range(), which > does also use get_flush_tlb_info(). > > We pass in PAGE_SHIFT here to ensure that the > stride shift is specified correctly to the > INVLPGB instruction later on. Hm I don't follow your answer here so lemme just state my current understanding more verbosely... flush_tlb_mm() indirectly calls get_flush_tlb_info() with end=TLB_FLUSH_ALL and stride_shift=0. That's an invalid stride shift, but this doesn't break anything because with TLB_FLUSH_ALL the stride shift is never used (except to check for values above PMD_SHIFT). So here I think passing stride_shift=0 would be fine too. Concretely, here we specifically call invlpgb_flush_all_nonglobals() which doesn't care about stride_shift, and flush_tlb_func() is the same as before this patchset in this respect. I would be quite happy with removing the "it's invalid but it doesn't matter" thing everywhere but this seems to be localised and I think the issue is orthogonal to the presence of invlpgb.