From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (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 8FF5E1F4262 for ; Thu, 20 Feb 2025 13:31:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740058309; cv=pass; b=evlxPHQYeFb4cwV7H0L9dQ8FG5Jf4sXH+LtPnz7sh3rYQM36JXuS7YJHxSxCeDVXbphXhMg23jDjTKwy7Vwu5Z8B4IkixRmyiCNGUH9xujRsxyShCoG6FLmoRzp8KXtqIXM1X59rl7dw0xsgIJg4KSr1w5jDWtkXRsSgMiEbY4Q= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740058309; c=relaxed/simple; bh=38UpxZeOUsXipbUwygCbrqOljhMT3i+SL0fC+IRIiNY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UnwHfnO701EmHcfuoANJbqD3EZdH72CyD2JTf4eBvM6s7KbmJFM6FfYJCco1KQYcPOBG7uRs/dI1JCFLbiLjuR4NGt4d1U9MO7O/WWvZ9LiOi89npbm4fvvE96NSfsVJ0OAKfKnuBY+QO7HsMx57RjotMN72DPDMh6HjvZbdUVg= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b=UXoL0xvt; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b="UXoL0xvt" ARC-Seal: i=1; a=rsa-sha256; t=1740058282; cv=none; d=zohomail.com; s=zohoarc; b=nZ+99W4l2bOwH34wjrLy0cykDdkPJYNYyEnfRIVnig2i8J8r+j2f9e0y30C9hLSucrchccpVIPt9Uad4Pjqi5nbXVv22R8ssGE4WmGwX4pBG/MyyM0wIpImqtBw95f8N5NZfJXJ/E1WZzMzVcRvfc6ufuUpSDhIuqsi5fimDcw4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1740058282; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=WwGtYpVbiHbXyNtzNp28/hsmWCNhDI4FpbukfWmffb0=; b=iefjYKVOzPMb3GNZCgitH+a2lYbiFWDw4Bcl3xX73CZw9VXUFjYVEQLjL8V6uetqHMNehd0zXeb7wOacMf6M/NR72Fp2ocfN0mr2VLCSqafXqV4Hd2c2fy55KTLbGx3cfodvL46iG3NVEbE8c5QxwvZusn+GisBHU8Z1lGjiSb4= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=dmitry.osipenko@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1740058282; s=zohomail; d=collabora.com; i=dmitry.osipenko@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=WwGtYpVbiHbXyNtzNp28/hsmWCNhDI4FpbukfWmffb0=; b=UXoL0xvtm1lIvSi8Qhx3+eUWHgoWc6aT95gQemoue/dUPAH5uIAJ59Wxr8AUxK4Q O53477u7GJjPs/aAThqhTxS4zQ0ghojo/vdGMtf5DM/o4b7VMWXm9640ZgsixJDsvYV YSbGscqSf2gKSTkPxE6L7OsNsie8FYZPqsv+DEPQ= Received: by mx.zohomail.com with SMTPS id 1740058280296164.49908263796294; Thu, 20 Feb 2025 05:31:20 -0800 (PST) Message-ID: Date: Thu, 20 Feb 2025 16:31:14 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 4/5] virtio-mmio: read shm region page size To: Sergio Lopez Pascual , "Michael S. Tsirkin" , Daniel Verkamp , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Simona Vetter , Rob Clark , fnkl.kernel@gmail.com Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20250214-virtio-shm-page-size-v2-0-aa1619e6908b@redhat.com> <20250214-virtio-shm-page-size-v2-4-aa1619e6908b@redhat.com> <1f9a86a5-97d6-41d5-9a30-0422fc9ec137@collabora.com> From: Dmitry Osipenko Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ZohoMailClient: External On 2/20/25 13:24, Sergio Lopez Pascual wrote: > Dmitry Osipenko writes: > >> On 2/14/25 18:16, Sergio Lopez wrote: >>> Use the newly introduced SHM_PAGE_SHIFT register to read the page shift >>> for the shared memory region, derive the page size from it and store the >>> resulting value into virtio_shm_region. >>> >>> Signed-off-by: Sergio Lopez >>> --- >>> drivers/virtio/virtio_mmio.c | 11 ++++++++++- >>> include/uapi/linux/virtio_mmio.h | 3 +++ >>> 2 files changed, 13 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c >>> index 1f594b626d7a7734e8ec58766737a118c26bad94..0f892770739ea84b3e7be5615332773049b10ab1 100644 >>> --- a/drivers/virtio/virtio_mmio.c >>> +++ b/drivers/virtio/virtio_mmio.c >>> @@ -537,6 +537,7 @@ static bool vm_get_shm_region(struct virtio_device *vdev, >>> struct virtio_shm_region *region, u8 id) >>> { >>> struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev); >>> + u8 page_shift = 0; >>> u64 len, addr; >>> >>> /* Select the region we're interested in */ >>> @@ -560,7 +561,15 @@ static bool vm_get_shm_region(struct virtio_device *vdev, >>> >>> region->addr = addr; >>> >>> - region->page_size = 4096; >>> + /* If supported by the device transport, read the region page size. >>> + * The page_shift variable is initialized to zero above, so if this >>> + * feature isn't supported it will result in a page_size of 4096, a >>> + * default safe value. >>> + */ >>> + if (__virtio_test_bit(vdev, VIRTIO_F_SHM_PAGE_SIZE)) >>> + page_shift = (u8) readl(vm_dev->base + VIRTIO_MMIO_SHM_PAGE_SHIFT); >>> + >>> + region->page_size = 1 << (page_shift + 12); >>> >>> return true; >>> } >>> diff --git a/include/uapi/linux/virtio_mmio.h b/include/uapi/linux/virtio_mmio.h >>> index 0650f91bea6c70f935764070d825d181a2379afb..43348be30eff90ee228b6490b9d3c35ba4c50aa5 100644 >>> --- a/include/uapi/linux/virtio_mmio.h >>> +++ b/include/uapi/linux/virtio_mmio.h >>> @@ -133,6 +133,9 @@ >>> #define VIRTIO_MMIO_SHM_BASE_LOW 0x0b8 >>> #define VIRTIO_MMIO_SHM_BASE_HIGH 0x0bc >>> >>> +/* Shared memory region page shift */ >>> +#define VIRTIO_MMIO_SHM_PAGE_SHIFT 0x0c4 >> >> What's the logic behind choosing 0x0c4, why not 0x0c0? > > It seems like Linux doesn't support it yet, but in the specs 0x0c0 is > already reserved for QueueReset. See QueueReset in the spec now, thanks. Reviewed-by: Dmitry Osipenko -- Best regards, Dmitry