From 4995734e973a2c2e9c6f6413cbad9913fc4df0dc Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 24 Jun 2016 09:07:39 -0700 Subject: [PATCH] acpi, nfit: fix acpi_check_dsm() vs zero functions implemented QEMU 2.6 implements nascent support for nvdimm DSMs. Depending on configuration it may only implement the function0 dsm to indicate that no other DSMs are available. Commit 31eca76ba2fc "nfit, libnvdimm: limited/whitelisted dimm command marshaling mechanism" breaks QEMU, but QEMU is spec compliant. Per the spec the way to indicate that no functions are supported is: If Function Index is zero, the return is a buffer containing one bit for each function index, starting with zero. Bit 0 indicates whether there is support for any functions other than function 0 for the specified UUID and Revision ID. If set to zero, no functions are supported (other than function zero) for the specified UUID and Revision ID. Update the nfit driver to determine the family (interface UUID) without requiring the implementation to define any other functions, i.e. short-circuit acpi_check_dsm() to succeed per the spec. The nfit driver appears to be the only user passing funcs==0 to acpi_check_dsm(), so this behavior change of the common routine should be limited to the probing done by the nfit driver. Cc: Len Brown Cc: Jerry Hoemann Acked-by: "Rafael J. Wysocki" Fixes: 31eca76ba2fc ("nfit, libnvdimm: limited/whitelisted dimm command marshaling mechanism") Reported-by: Xiao Guangrong Tested-by: Xiao Guangrong Signed-off-by: Dan Williams --- drivers/acpi/nfit.c | 6 +++--- drivers/acpi/utils.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c index 2215fc847fa9..32579a7b71d5 100644 --- a/drivers/acpi/nfit.c +++ b/drivers/acpi/nfit.c @@ -1131,11 +1131,11 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc, /* * Until standardization materializes we need to consider up to 3 - * different command sets. Note, that checking for function0 (bit0) - * tells us if any commands are reachable through this uuid. + * different command sets. Note, that checking for zero functions + * tells us if any commands might be reachable through this uuid. */ for (i = NVDIMM_FAMILY_INTEL; i <= NVDIMM_FAMILY_HPE2; i++) - if (acpi_check_dsm(adev_dimm->handle, to_nfit_uuid(i), 1, 1)) + if (acpi_check_dsm(adev_dimm->handle, to_nfit_uuid(i), 1, 0)) break; /* limit the supported commands to those that are publicly documented */ diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c index 22c09952e177..b4de130f2d57 100644 --- a/drivers/acpi/utils.c +++ b/drivers/acpi/utils.c @@ -680,9 +680,6 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, u64 rev, u64 funcs) u64 mask = 0; union acpi_object *obj; - if (funcs == 0) - return false; - obj = acpi_evaluate_dsm(handle, uuid, rev, 0, NULL); if (!obj) return false; @@ -695,6 +692,9 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, u64 rev, u64 funcs) mask |= (((u64)obj->buffer.pointer[i]) << (i * 8)); ACPI_FREE(obj); + if (funcs == 0) + return true; + /* * Bit 0 indicates whether there's support for any functions other than * function 0 for the specified UUID and revision.