From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 52C432DAFDE; Tue, 28 Apr 2026 15:20:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777389636; cv=none; b=Et2MCTY7KlmQP6hkJu6miCDqTKl5VtR9+IQbnNQeC1T/O0unUcpvHtA3e+G3DLnaDGJu7e0oAZNPmCWcAXi/nTFnwsOcgxs2wEjIHDZhulA8L8wBDkTVxDtiMC9zOCI/92URTRNnzztYCZNkqmtBpD17OUA6sdUBDzfHyk731bI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777389636; c=relaxed/simple; bh=Idtctt/kb/SmoiGHu5ljVhs/2lxRvfaLWYLp4lxeqbo=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=jAHlwdM27Ynq0jRe8DWnlKJ4EYERDITggWHTAH0hB/bKXPHgWfacgoorHpcU6MQmjXci85ks1XhSVkJ9qUdxKu5usIZPeGoVeZQwn1FxHtTy4g5RYUhDf78JeUanmKowX5x/DweJCD86exJpnVnSqSsGdIZ8YP+lFc6h23ahF0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DvBcYKMC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DvBcYKMC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0804C2BCAF; Tue, 28 Apr 2026 15:20:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777389635; bh=Idtctt/kb/SmoiGHu5ljVhs/2lxRvfaLWYLp4lxeqbo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=DvBcYKMCG6re7fgbFGsln5FXGziuiyoQxC1feSafGl9EQxtJLZf0q9Rx00qUdXPUD OeYusMPopskeKZvt0fIXKQzPoDnVc9IaiWtvkO6Qvp6b6af0vo+cySgrhNlI1d4ck6 DMTv2W1296lNOpd6QX9pNyqJgwpBegzB/ifpdo5SmPIv8ToeLQaM+j8ccSvgho8bxr lBs2OpeDbVTUwgaBJjzZ8+5vv4RCB9Bct9tVAbsPkIko0LEuZCxdQtTG/NCv8s+VYZ f1te80WvDZ/zoBeDAu6sz6EVYotX+MbXZI/LgGqvIAFQ5/H9B+WOCIkSHUx0h8lDRU 1kx0GQNYUhecg== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1wHkEj-0000000FYlQ-1LxN; Tue, 28 Apr 2026 15:20:33 +0000 Date: Tue, 28 Apr 2026 16:20:32 +0100 Message-ID: <86pl3jyuv3.wl-maz@kernel.org> From: Marc Zyngier To: Sascha Bischoff Cc: "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "kvm@vger.kernel.org" , nd , "oliver.upton@linux.dev" , Joey Gouly , Suzuki Poulose , "yuzenghui@huawei.com" , "peter.maydell@linaro.org" , "lpieralisi@kernel.org" , Timothy Hayes Subject: Re: [PATCH 05/43] KVM: arm64: gic-v5: Extract host IRS caps from IRS config frame In-Reply-To: <20260427160547.3129448-6-sascha.bischoff@arm.com> References: <20260427160547.3129448-1-sascha.bischoff@arm.com> <20260427160547.3129448-6-sascha.bischoff@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvm@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=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: Sascha.Bischoff@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, nd@arm.com, oliver.upton@linux.dev, Joey.Gouly@arm.com, Suzuki.Poulose@arm.com, yuzenghui@huawei.com, peter.maydell@linaro.org, lpieralisi@kernel.org, Timothy.Hayes@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Mon, 27 Apr 2026 17:07:44 +0100, Sascha Bischoff wrote: > > The host irqchip driver provides KVM with a pointer to an IRS's config > frame, which allows KVM to directly interact with the host's IRS. The > MMIO registers in the config frame are used to configure VMs (in > addition to them being used by the host). The IRS's config frame also > includes a set of ID registers which describe the capabilities that > the IRS has. > > Stash the pointer to the config frame, and extract the VM capabilities > (from IRS_IDR3 & IRS_IDR4), as well as the IST > capabilities/requirements (IRS_IDR2) from the IRS. > > Signed-off-by: Sascha Bischoff > --- > arch/arm64/kvm/Makefile | 2 +- > arch/arm64/kvm/vgic/vgic-v5-tables.c | 8 +++++ > arch/arm64/kvm/vgic/vgic-v5-tables.h | 41 ++++++++++++++++++++++ > arch/arm64/kvm/vgic/vgic-v5.c | 52 ++++++++++++++++++++++++++++ > include/linux/irqchip/arm-gic-v5.h | 10 ++++++ > 5 files changed, 112 insertions(+), 1 deletion(-) > create mode 100644 arch/arm64/kvm/vgic/vgic-v5-tables.c > create mode 100644 arch/arm64/kvm/vgic/vgic-v5-tables.h > > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > index 59612d2f277c1..431de9b145ca1 100644 > --- a/arch/arm64/kvm/Makefile > +++ b/arch/arm64/kvm/Makefile > @@ -24,7 +24,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \ > vgic/vgic-mmio.o vgic/vgic-mmio-v2.o \ > vgic/vgic-mmio-v3.o vgic/vgic-kvm-device.o \ > vgic/vgic-its.o vgic/vgic-debug.o vgic/vgic-v3-nested.o \ > - vgic/vgic-v5.o > + vgic/vgic-v5.o vgic/vgic-v5-tables.o > > kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o > kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o > diff --git a/arch/arm64/kvm/vgic/vgic-v5-tables.c b/arch/arm64/kvm/vgic/vgic-v5-tables.c > new file mode 100644 > index 0000000000000..30e2b108b1aa3 > --- /dev/null > +++ b/arch/arm64/kvm/vgic/vgic-v5-tables.c > @@ -0,0 +1,8 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2025, 2026 Arm Ltd. > + */ > + > +#include "vgic-v5-tables.h" > + > +struct vgic_v5_host_ist_caps gicv5_host_ist_caps; > diff --git a/arch/arm64/kvm/vgic/vgic-v5-tables.h b/arch/arm64/kvm/vgic/vgic-v5-tables.h > new file mode 100644 > index 0000000000000..cf00a248eabd5 > --- /dev/null > +++ b/arch/arm64/kvm/vgic/vgic-v5-tables.h > @@ -0,0 +1,41 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2025, 2026 Arm Ltd. > + */ > + > +#ifndef __KVM_ARM_VGICV5_TABLES_H__ > +#define __KVM_ARM_VGICV5_TABLES_H__ > + > +#include > + > +struct vgic_v5_host_ist_caps { > + /* IST Capabilities */ > + > + /* Apply to LPIs and SPIs */ > + u8 ist_id_bits; > + bool ist_levels; > + u8 ist_l2sz; > + bool istmd; > + u8 istmd_sz; > + > + /* LPI only */ > + u8 min_lpi_id_bits; > + > + /* VM Table, VPE Table */ > + bool two_level_vmt_support; > + u32 max_vms; > + u32 max_vpes; > + u16 vmd_size; > + u16 vped_size; > + > + /* Is the IRS coherent with us, or not? */ > + bool irs_non_coherent; > +}; > + > +extern struct vgic_v5_host_ist_caps gicv5_host_ist_caps; > +static inline struct vgic_v5_host_ist_caps *vgic_v5_host_caps(void) > +{ > + return &gicv5_host_ist_caps; > +} Err. No. Make gicv5_host_ist_caps static, and move the helper as non-inline in vgic-v5-tables.c. It's not like this is anywhere near performance-critical stuff, is it? But also, if that's global information, we have kvm_vgic_global_state. Isn't that where these things should live? Then the introduction of vgic-v5-tables.[ch] can be moved to the point where it actually matters. > + > +#endif > diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c > index d4789ff3e7402..fd3d6299a2baa 100644 > --- a/arch/arm64/kvm/vgic/vgic-v5.c > +++ b/arch/arm64/kvm/vgic/vgic-v5.c > @@ -9,6 +9,7 @@ > #include > > #include "vgic.h" > +#include "vgic-v5-tables.h" > > #define ppi_caps kvm_vgic_global_state.vgic_v5_ppi_caps > > @@ -34,6 +35,54 @@ static void vgic_v5_get_implemented_ppis(void) > __assign_bit(GICV5_ARCH_PPI_PMUIRQ, ppi_caps.impl_ppi_mask, system_supports_pmuv3()); > } > > +static void __iomem *irs_base; Global state? > + > +static u32 irs_readl_relaxed(const u32 reg_offset) > +{ > + return readl_relaxed(irs_base + reg_offset); > +} > + > +static int gicv5_irs_extract_vm_caps(const struct gic_kvm_info *info) > +{ > + u64 idr; > + > + irs_base = info->gicv5_irs.base; > + if (!irs_base) { > + kvm_info("No GICv5 MMIO IRS address; no GICv5 support\n"); > + return -ENODEV; > + } Should you instead bail out early by not registering the gic_kvm_info when the IRS base is unknown, making this sort of checks irrelevant? Also, it's not like we can make it very far without an IRS... > + > + vgic_v5_host_caps()->irs_non_coherent = info->gicv5_irs.non_coherent; > + > + idr = irs_readl_relaxed(GICV5_IRS_IDR2); > + > + /* We skip the LPI field as it only applies to physical LPIs */ > + vgic_v5_host_caps()->ist_id_bits = FIELD_GET(GICV5_IRS_IDR2_ID_BITS, idr); > + vgic_v5_host_caps()->min_lpi_id_bits = FIELD_GET(GICV5_IRS_IDR2_MIN_LPI_ID_BITS, idr); > + vgic_v5_host_caps()->ist_levels = !!FIELD_GET(GICV5_IRS_IDR2_IST_LEVELS, idr); > + vgic_v5_host_caps()->ist_l2sz = FIELD_GET(GICV5_IRS_IDR2_IST_L2SZ, idr); > + vgic_v5_host_caps()->istmd = !!FIELD_GET(GICV5_IRS_IDR2_ISTMD, idr); > + vgic_v5_host_caps()->istmd_sz = FIELD_GET(GICV5_IRS_IDR2_ISTMD_SZ, idr); > + > + idr = irs_readl_relaxed(GICV5_IRS_IDR3); > + > + vgic_v5_host_caps()->max_vms = BIT(FIELD_GET(GICV5_IRS_IDR3_VM_ID_BITS, idr)); > + vgic_v5_host_caps()->two_level_vmt_support = !!FIELD_GET(GICV5_IRS_IDR3_VMT_LEVELS, idr); > + > + if (FIELD_GET(GICV5_IRS_IDR3_VMD, idr)) The constant (ab)use of FIELD_GET() for fields that are single bit wide is very hard to read. I'd like to see: vgic_v5_host_caps()->ist_levels = (idr & GICV5_IRS_IDR2_IST_LEVELS); [...] vgic_v5_host_caps()->istmd = (idr & GICV5_IRS_IDR2_ISTMD); [...] if (idr & GICV5_IRS_IDR3_VMD) [...] which is infinitely more readable. > + vgic_v5_host_caps()->vmd_size = BIT(FIELD_GET(GICV5_IRS_IDR3_VMD_SZ, idr)); > + else > + vgic_v5_host_caps()->vmd_size = 0; > + > + idr = irs_readl_relaxed(GICV5_IRS_IDR4); > + > + vgic_v5_host_caps()->vped_size = BIT(FIELD_GET(GICV5_IRS_IDR4_VPED_SZ, idr)); > + /* Field stores VPE_ID_BITS - 1 */ > + vgic_v5_host_caps()->max_vpes = BIT(FIELD_GET(GICV5_IRS_IDR4_VPE_ID_BITS, idr) + 1); > + > + return 0; > +} > + > /* > * Probe for a vGICv5 compatible interrupt controller, returning 0 on success. > */ > @@ -61,6 +110,9 @@ int vgic_v5_probe(const struct gic_kvm_info *info) > goto skip_v5; > } > > + if (gicv5_irs_extract_vm_caps(info)) > + goto skip_v5; > + We shouldn't "skip_v5" anymore. If we can't initialise KVM with GICv5, we're done, and we should not even try to register v3. Thanks, M. -- Without deviation from the norm, progress is not possible.