From: Sasha Levin Date: Sun, 10 Jan 2021 13:18:37 +0000 (-0500) Subject: Fixes for 5.4 X-Git-Tag: v4.4.251~34 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=dec253cc4519788993f907bd406acbee21ed9f85;p=thirdparty%2Fkernel%2Fstable-queue.git Fixes for 5.4 Signed-off-by: Sasha Levin --- diff --git a/queue-5.4/series b/queue-5.4/series index 8ae3b1ab884..f7652e9c096 100644 --- a/queue-5.4/series +++ b/queue-5.4/series @@ -45,3 +45,4 @@ ionic-account-for-vlan-tag-len-in-rx-buffer-len.patch net-sched-sch_taprio-ensure-to-reset-destroy-all-child-qdiscs.patch kbuild-don-t-hardcode-depmod-path.patch bluetooth-revert-hci_h5-close-serdev-device-and-free-hu-in-h5_close.patch +video-hyperv_fb-fix-the-mmap-regression-for-v5.4.y-a.patch diff --git a/queue-5.4/video-hyperv_fb-fix-the-mmap-regression-for-v5.4.y-a.patch b/queue-5.4/video-hyperv_fb-fix-the-mmap-regression-for-v5.4.y-a.patch new file mode 100644 index 00000000000..2e5c59c303b --- /dev/null +++ b/queue-5.4/video-hyperv_fb-fix-the-mmap-regression-for-v5.4.y-a.patch @@ -0,0 +1,76 @@ +From 1063eb353a4044dcbf0219889c51c77e3f12966a Mon Sep 17 00:00:00 2001 +From: Sasha Levin +Date: Sat, 9 Jan 2021 14:53:58 -0800 +Subject: video: hyperv_fb: Fix the mmap() regression for v5.4.y and older +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +From: Dexuan Cui + +db49200b1dad is backported from the mainline commit +5f1251a48c17 ("video: hyperv_fb: Fix the cache type when mapping the VRAM"), +to v5.4.y and older stable branches, but unluckily db49200b1dad causes +mmap() to fail for /dev/fb0 due to EINVAL: + +[ 5797.049560] x86/PAT: a.out:1910 map pfn expected mapping type + uncached-minus for [mem 0xf8200000-0xf85cbfff], got write-back + +This means the v5.4.y kernel detects an incompatibility issue about the +mapping type of the VRAM: db49200b1dad changes to use Write-Back when +mapping the VRAM, while the mmap() syscall tries to use Uncached-minus. +That’s to say, the kernel thinks Uncached-minus is incompatible with +Write-Back: see drivers/video/fbdev/core/fbmem.c: fb_mmap() -> +vm_iomap_memory() -> io_remap_pfn_range() -> ... -> track_pfn_remap() -> +reserve_pfn_range(). + +Note: any v5.5 and newer kernel doesn't have the issue, because they +have commit +d21987d709e8 ("video: hyperv: hyperv_fb: Support deferred IO for Hyper-V frame buffer driver") +, and when the hyperv_fb driver has the deferred_io support, +fb_deferred_io_init() overrides info->fbops->fb_mmap with +fb_deferred_io_mmap(), which doesn’t check the mapping type +incompatibility. Note: since it's VRAM here, the checking is not really +necessary. + +Fix the regression by ioremap_wc(), which uses Write-combining. The kernel +thinks it's compatible with Uncached-minus. The VRAM mappped by +ioremap_wc() is slightly slower than mapped by ioremap_cache(), but is +still significantly faster than by ioremap(). + +Change the comment accordingly. Linux VM on ARM64 Hyper-V is still not +working in the latest mainline yet, and when it works in future, the ARM64 +support is unlikely to be backported to v5.4 and older, so using +ioremap_wc() in v5.4 and older should be ok. + +Note: this fix is only targeted at the stable branches: +v5.4.y, v4.19.y, v4.14.y, v4.9.y and v4.4.y. + +Fixes: db49200b1dad ("video: hyperv_fb: Fix the cache type when mapping the VRAM") +Signed-off-by: Dexuan Cui +Signed-off-by: Sasha Levin +--- + drivers/video/fbdev/hyperv_fb.c | 6 ++---- + 1 file changed, 2 insertions(+), 4 deletions(-) + +diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c +index 81671272aa58f..1c6ae98710a01 100644 +--- a/drivers/video/fbdev/hyperv_fb.c ++++ b/drivers/video/fbdev/hyperv_fb.c +@@ -704,11 +704,9 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info) + } + + /* +- * Map the VRAM cacheable for performance. This is also required for +- * VM Connect to display properly for ARM64 Linux VM, as the host also +- * maps the VRAM cacheable. ++ * Map the VRAM cacheable for performance. + */ +- fb_virt = ioremap_cache(par->mem->start, screen_fb_size); ++ fb_virt = ioremap_wc(par->mem->start, screen_fb_size); + if (!fb_virt) + goto err2; + +-- +2.27.0 +