It was brought to our attention that some MMC host drivers are referencing sg_virt(sg) directly on scatterlist entries, which will not perform buffer bouncing for CONFIG_HIGHMEM pages that reside in highmem. See the following mail from Christoph and the discussion: https://lore.kernel.org/linux-mmc/20240122073423.GA25859@xxxxxx/ This means that bugs with highmem pages can go unnoticed until an actual highmem page is finally used and not bounced, resulting in things like unpredictable file corruption. Attempt to fix this by amending all host controllers calling sg_virt() for PIO to instead do proper mapping and unmapping of the scatterlist entry, possibly bouncing it from highmem if need be. More complicated patches are possible, the most obvious to rewrite the PIO loops to use sg_miter_[start|next|stop]() see for example mmci.c, but I leave this refactoring as a suggestion to each device driver maintainer because I can't really test the patches. All patches are compile-tested except the m68k one, sdhci-esdhc-mcf. Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> --- Linus Walleij (7): mmc: davinci_mmc: Map the virtual page for PIO mmc: moxart-mmc: Map the virtual page for PIO mmc: mvsdio: Map the virtual page for PIO mmc: mxcmmc: Map the virtual page for PIO mmc: omap: Map the virtual page for PIO mmc: sdhci-esdhc-mcf: Map the virtual page for swapping mmc: sh_mmcif: Map the virtual page for PIO drivers/mmc/host/davinci_mmc.c | 10 ++++++++-- drivers/mmc/host/moxart-mmc.c | 3 ++- drivers/mmc/host/mvsdio.c | 3 ++- drivers/mmc/host/mxcmmc.c | 23 +++++++++++++++-------- drivers/mmc/host/omap.c | 7 ++++++- drivers/mmc/host/sdhci-esdhc-mcf.c | 3 ++- drivers/mmc/host/sh_mmcif.c | 22 ++++++++++++++++++---- 7 files changed, 53 insertions(+), 18 deletions(-) --- base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d change-id: 20240125-mmc-proper-kmap-f2d4cf5d1756 Best regards, -- Linus Walleij <linus.walleij@xxxxxxxxxx>
