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Mon, 16 Sep 2024 07:16:08 +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 qWQ2Izjb52b0KAAAD6G6ig (envelope-from ); Mon, 16 Sep 2024 07:16:08 +0000 Date: Mon, 16 Sep 2024 09:16:58 +0200 Message-ID: <874j6g9ifp.wl-tiwai@suse.de> From: Takashi Iwai To: Christoph Hellwig Cc: Andrew Cooper , Ariadne Conill , xen-devel@lists.xenproject.org, alsa-devel@alsa-project.org, stable@vger.kernel.org Subject: Re: [PATCH] Revert "ALSA: memalloc: Workaround for Xen PV" In-Reply-To: References: <20240906184209.25423-1-ariadne@ariadne.space> <877cbnewib.wl-tiwai@suse.de> <9eda21ac-2ce7-47d5-be49-65b941e76340@citrix.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-3.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCPT_COUNT_FIVE(0.00)[6]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid] X-Spam-Score: -3.30 X-Spam-Flag: NO On Thu, 12 Sep 2024 11:56:21 +0200, Christoph Hellwig wrote: > > On Sat, Sep 07, 2024 at 11:38:50AM +0100, Andrew Cooper wrote: > > Individual subsystems ought not to know or care about XENPV; it's a > > layering violation. > > Agreed. > > > If the main APIs don't behave properly, then it probably means we've got > > a bug at a lower level (e.g. Xen SWIOTLB is a constant source of fun) > > which is probably affecting other subsystems too. > > > > I think we need to re-analyse the original bug.  Right now, the > > behaviour resulting from 53466ebde is worse than what it was trying to fix. > > 53466ebde looks bogus to me, and the commit message doesn't even > try to explain what bad behavior it works around. I'd also like to > state once again that if you think something is broken about dma > allocation or mapping helpers please Cc me and the iommu list. > > Most of the time it's actually the drivers doing something invalid, but > sometimes it is a core dma layer bug or something that needs a proper > API. > > Also while looking at the above commit I noticed the broken fallback > code in snd_dma_noncontig_alloc - get_dma_ops is not for driver use, > and starting with the code queued up for 6.12 will also return NULL > when using dma-iommu for example. Yes, all those are really ugly hacks and have been already removed for 6.12. Let's hope everything works as expected with it. thanks, Takashi