Re: [PATCH v19 3/7] firmware: arm_rmm: Configure the RMM with the host's page size
flat view
From: Jonathan Cameron <hidden>
Date: 2026-09-24 17:03:23
Also in:
kvm, kvmarm, linux-coco, lkml
On Thu, 24 Sep 2026 14:51:57 +0100 Suzuki K Poulose [off-list ref] wrote:
RMM v2.0 brings the ability to set the RMM's granule size. Check the feature registers and configure the RMM so that it matches the host's page size. This means that operations can be done with a granularity equal to PAGE_SIZE. Signed-off-by: Steven Price <steven.price@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Hi Suzuki, Some trivial stuff inline. Assuming that is addressed. Reviewed-by: Jonathan Cameron <redacted>
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--- drivers/firmware/arm_rmm/rmi.c | 70 ++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+)diff --git a/drivers/firmware/arm_rmm/rmi.c b/drivers/firmware/arm_rmm/rmi.c index 3baba931f92e4..c9ea964fd9081 100644 --- a/drivers/firmware/arm_rmm/rmi.c +++ b/drivers/firmware/arm_rmm/rmi.c
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+ +static int rmi_configure(void) +{ + unsigned long granule_feature; + unsigned long granule_size; + int ret = 0;
Value not used. Fine if it is future churn reduction, but I didn't spot where if so. I'm guessing left over from refactoring
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+ + switch (PAGE_SIZE) { + case SZ_4K: + granule_size = RMI_GRANULE_SIZE_4KB; + granule_feature = RMI_FEATURE_REGISTER_1_RMI_GRAN_SZ_4KB; + break; + case SZ_16K: + granule_size = RMI_GRANULE_SIZE_16KB; + granule_feature = RMI_FEATURE_REGISTER_1_RMI_GRAN_SZ_16KB; + break; + case SZ_64K: + granule_size = RMI_GRANULE_SIZE_64KB; + granule_feature = RMI_FEATURE_REGISTER_1_RMI_GRAN_SZ_64KB; + break; + default: + BUILD_BUG(); + } + + if (!(rmi_feat_reg(1) & granule_feature)) { + pr_err("RMM does not support %luKB granules\n", + PAGE_SIZE >> 10); + return -ENXIO; + } + + struct rmm_config *config __free(free_page) = + (struct rmm_config *)get_zeroed_page(GFP_KERNEL); + + if (!config) { + pr_err("Unable to allocate memory for RMM config\n"); + return -ENOMEM; + } + + config->rmi_granule_size = granule_size; + + /* + * For now we set the tracking_region_size to 0 which is the only option + * for 4KB PAGE_SIZE (1GB for 4KB PAGE_SIZE, 32MB/512MB for 16KB/64KB). + * TODO: Support other tracking sizes via Kconfig option for other + * PAGE_SIZES + */ + config->tracking_region_size = 0; + + ret = rmi_rmm_config_set(virt_to_phys(config)); + if (ret) { + pr_err("RMM config set failed (%d)\n", ret); + ret = -EINVAL;
return -EINVAL;
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+ } + + return ret;
return 0; So obvious this is the good path without anyone having to think about it! I did quick check on whether this was to reduce churn due to later changes but couldn't immediately spot anything
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