From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender3-of-o54.zoho.com (sender3-of-o54.zoho.com [136.143.184.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F38631A808; Wed, 26 Nov 2025 08:52:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.184.54 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764147154; cv=pass; b=pTHBZKc57OgZmgn8anKkH5rqsCEdAg5cumt3VG4VH/Llv71IljzkF9VViiecAwlHwqPxc3AhzWvlyjOGrMpiqBZuQ3mdjfVBL/E4/k+NkL3lYP66oMokroT4fi53aTne7c3M226LlfhQqD/lyaOqiBSECONoKZlyGTPCVM8PByo= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764147154; c=relaxed/simple; bh=7bqK9leSbZJO6WeM9sl8N4am2gpal5/ZjQs4k51+4GE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MlmnaHE2GIkv4Wf/lnfu2k7ceJ9MkH3zNptE+yKIDG3BgrMgzPTcZTJJu+m8aW6wc7v4AE4RXGi5cmVnyHreQemC7pc+3TY1xSPgnOphP2U3KzaN7swsyPPhxIF/ZASro3TNIbZwOhklS6v+JqJH0cNvJlJA22EXSmI4+YkwFGc= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=anirudhrb.com; spf=pass smtp.mailfrom=anirudhrb.com; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b=AzWGxEIN; arc=pass smtp.client-ip=136.143.184.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b="AzWGxEIN" ARC-Seal: i=1; a=rsa-sha256; t=1764147129; cv=none; d=zohomail.com; s=zohoarc; b=EozE+DQrrfnCJQj1hNrK39Qej1ArM2OEIOAdUb9dYdn4ekF/mV6GCULrPHmc+HXFeUDf91WkI1WLUk5M+antVsx8OhxVU97UOIWlE9JXQJvTPv+g7O4CTRFWcGE32iBNLOaLQ1SXZqXVFyhG+GOIYjD0XEhgpCJKy6UgxD+0gf8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1764147129; h=Content-Type:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=4kMxEju5M/nKc9DOThZPJgB81pFJ1BBy6AQBjiH7yQ8=; b=XO/k7zRjvg5DJES+Z7O4fBVDcXkr495nzZ2gZiefk84q4eMNybbNzMS1+a5fk4/gVJVmbBLAChWpiq9pG+X3VuyikUTiwHT+JP4jsCcWjkXr/oqE5um5IzX3X6eko3IZj8wTSXFxZXBTMwVmyZ9eNMol2L9Un8zIxvZKuldfur0= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=anirudhrb.com; spf=pass smtp.mailfrom=anirudh@anirudhrb.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1764147128; s=zoho; d=anirudhrb.com; i=anirudh@anirudhrb.com; h=Date:Date:From:From:To:To:Cc:Cc:Subject:Subject:Message-ID:References:MIME-Version:Content-Type:In-Reply-To:Message-Id:Reply-To; bh=4kMxEju5M/nKc9DOThZPJgB81pFJ1BBy6AQBjiH7yQ8=; b=AzWGxEINhyaf9Qe+BWKH+NZJVrxv8NBMjcNINDPYzYvRpgYVKYnnKEYrqYkUdDtv z7qjNz41mKXNNgDt3cgB04f4MvxZhrGhjZZoDuxIvmjrITReaIHHMPsZkjYXkxd7ZAF 15eQYl9dVfhiZaVJGab8YnaExsH59ZlBynzqldzQ= Received: by mx.zohomail.com with SMTPS id 1764147125272486.14699736135515; Wed, 26 Nov 2025 00:52:05 -0800 (PST) Date: Wed, 26 Nov 2025 08:51:59 +0000 From: Anirudh Rayabharam To: Marc Zyngier Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, Arnd Bergmann , akpm@linux-foundation.org, agordeev@linux.ibm.com, guoweikang.kernel@gmail.com, osandov@fb.com, bsz@amazon.de, linux-hyperv@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 2/3] irqchip/gic-v3: allocate one SGI for MSHV Message-ID: References: <20251125170124.2443340-1-anirudh@anirudhrb.com> <20251125170124.2443340-3-anirudh@anirudhrb.com> <86bjkqq9dp.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86bjkqq9dp.wl-maz@kernel.org> X-ZohoMailClient: External On Tue, Nov 25, 2025 at 06:01:38PM +0000, Marc Zyngier wrote: > On Tue, 25 Nov 2025 17:01:23 +0000, > Anirudh Raybharam wrote: > > > > From: Anirudh Rayabharam > > > > From: Anirudh Rayabharam (Microsoft) > > > > Currently SGIs are allocated only for the smp subsystem. The MSHV > > (Microsoft Hypervisor aka Hyper-V) code also needs an SGI that can be > > programmed into the SYNIC to receive intercepts from the hypervisor. The > > hypervisor would then assert this SGI whenever there is a guest > > VMEXIT. > > > > Allocate one SGI for MSHV use in addition to the SGIs allocated for > > IPIs. When running under MSHV, the full SGI range can be used i.e. no > > need to reserve SGIs 8-15 for the secure firmware. > > > > Since this SGI is needed only when running as a parent partition (i.e. > > we can create guest partitions), check for it before allocating an SGI. > > Sorry, but that's not an acceptable situation. > > SGIs are for Linux to use, nobody else, and that allocation must be Why does this restriction exist? In the code SGIs 8-15 are left for secure firmware. So, things other than Linux can use SGIs. Why not MSHV then? > the same irrespective of whether Linux runs virtualised or not. This > also won't work with GICv5 (there are no SGIs at all), so this is > doomed from the very start, and would immediately create technical > debt. Hyper-V always presents a GICv3 so we don't need to worry about GICv5. > > If you want to signal an interrupt to Linux, expose a device with an > interrupt in a firmware table (i.e. not an SGI), and use that in your > driver. You mean in the ACPI tables? That would require us to modify the firmware to expose this virtual device right? Anirudh. > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible.