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Wed, 19 Mar 2025 15:23:40 +0000 (UTC) Date: Wed, 19 Mar 2025 16:23:34 +0100 From: Borislav Petkov To: Junaid Shahid Cc: Brendan Jackman , akpm@linux-foundation.org, dave.hansen@linux.intel.com, yosryahmed@google.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, peterz@infradead.org, seanjc@google.com, tglx@linutronix.de, x86@kernel.org Subject: Re: [PATCH RFC v2 03/29] mm: asi: Introduce ASI core API Message-ID: <20250319152334.GLZ9rhdrBYW2yXRbY3@fat_crate.local> References: <20250227120607.GPZ8BVL2762we1j3uE@fat_crate.local> <20250228084355.2061899-1-jackmanb@google.com> <20250314131419.GJZ9Qrq8scAtDyBUcg@fat_crate.local> <5aa114f7-3efb-4dab-8579-cb9af4abd3c0@google.com> <20250315123621.GCZ9V0RWGFapbQNL1w@fat_crate.local> <4ce0b11c-d2fd-4dff-b9db-30e50500ee83@google.com> <14f9106d-3a34-4f10-ba4e-465c73c94eba@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <14f9106d-3a34-4f10-ba4e-465c73c94eba@google.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 99183160008 X-Stat-Signature: zctzgxjq7ip3rkgdy5gy8rg9tmw6twfy X-HE-Tag: 1742397839-277636 X-HE-Meta: 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 t7IXgP51 tSBELIDipgvn4lScz16FmwlhhF1KDFyl+drnzZiFdkkBNAF3KyQqEbTLGwXZrdVzBgS9olVb54aZmGk6WhGqJFlkefOocR55TSTV+6lbVfXVE1JcV/b5IvVZIR1ZakAqg7Schfr0IbLM/T7gHXTjT0a0fzioVZGMj8zTOpzyV+EPpFho7bOXS7XJsyDNdEdlpW/zvRDIXaySoiRmrX84QURADPXuhzSDNrw7/g5rQtWw4Js6AleUhvvI9V9V8VeSx9BG8rDUOvgEr8E0m+NDtBt9te8dlTBW3Pe19jn3n8XWFPqsXY90FngFuWOIQ8IdBlTPN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000155, 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 Tue, Mar 18, 2025 at 03:48:47PM -0700, Junaid Shahid wrote: > > Oh. Yeah. In my proposal below I had totally forgotten we had > > asi_exit() in the context_switch() path (it is there in this patch). > > > > So we only need the asi_exit() in the KVM code in order to avoid > > actually hitting e.g. exit_to_user_mode() in the restricted address > > space. > > > > But... we can just put an asi_exit() there explicitly instead of > > dumping all this weirdness into the "core API" and the KVM codebase. > > > > So... I think all we really need is asi_start_critical() and > > asi_end_critical()? And make everything else happen as part of the > > normal functioning of the entry and context-switching logic. Am I > > forgetting something else? > > Yes, I think this should work. Ok, what I read so far makes sense to me. That thing - modulo simplification but even without it - is kinda clear and straight-forward: ioctl(KVM_RUN) { enter_from_user_mode() asi_start() while !need_userspace_handling() asi_start_critical(); vmenter(); asi_end_critical(); } asi_end() exit_to_user_mode() } Lemme continue through the set. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette